Bio 283 Ch 8, Genetics Chapter 8, Genetics Final

25 July 2022
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question
Additional copies of a gene ___ (sometimes, always, never) cause cellular problems.
answer
Sometimes
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The spread of a complete metaphase chromosome set presented for diagnostic purposes is called a _____ (translocation, genome, karyotype, polyploidy)
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Karyotype
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Failure to separate for homologous chromosomes or sister chromatids is referred to as _______.
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Nondisjunction
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Of all cases of primary Down syndrome, 92% is caused by _______.
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Trisomy
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________ is a type of polyploidy that arises from the hybridization between two different species.
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Allopolyploidy
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Which of the following statements about chromosome inversions is correct? Chromosome inversions can reduce the number of chromosomes in a cell. Chromosome inversions lead to an increase in crossovers. Chromosome inversions do not affect gene expression. Chromosome inversions flip a segment of a chromosome 180 degrees.
answer
Chromosome inversions flip a segment of a chromosome 180 degrees.
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Which of the following statements about chromosome translocation is correct? Translocations only take place within a chromosome. Translocation and "crossing over" refer to the same phenomenon. Translocation can affect gene expression by moving a gene under the control of a different promoter. Translocations do not affect chromosome number.
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Translocation can affect gene expression by moving a gene under the control of a different promoter.
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Match the definitions to the appropriate terms that describe the number of chromosomes. Four homologues of each chromosome
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Tetraploid
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Match the definitions to the appropriate terms that describe the number of chromosomes. Two extra copies of a specific chromosome
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Tetrasomic
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Match the definitions to the appropriate terms that describe the number of chromosomes. A genome composed of four unique chromosomes
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n=4
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The Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings. Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Determine the phenotypes and proportions of progeny produced by the cross. A. Red eyed Notch female x White Eyed Male
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1/3 Wild Type Males, 1/3 Wild Type Females, 1/3 White Eyed Notch Females
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The Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings. Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Determine the phenotypes and proportions of progeny produced by the cross. B. White Eyed Notch Female x Red Eyed Male
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1/3 Red Eyed Notch Females, 1/3 Wild Type Females, 1/3 White Eyed Males
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The Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings. Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Determine the phenotypes and proportions of progeny produced by the cross. C. White Eyed Notch Female x White Eyed Male
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1/3 White Eyed Females, 1/3 White Eyed Notch Females, 1/3 White Eyed Males
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Select the statements that explain why duplication is a driving force for evolution and the generation of new genes. 1. Genes duplicate and then diverge from the original sequence to create multigene families. 2. Phenotypic variations can occur when random fixed mutations are introduced into a new chromosomal environment. 3. Duplication of a gene segment always results in novel phenotypes. 4. Duplicated genes provide extra copies of DNA that are not constrained by an essential function.
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1, 2 and 4
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Two brothers have X-linked red-green colorblind vision, and their parents have normal color vision. The first brother's karyotype is 47,XXY (Klinefelter syndrome), and the second brother's karyotype is 46,XY. In which parent and in what cell division phase did the first brother's chromosomal nondisjunction occur? Assume no recombination.
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Meiosis II in the mother
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A man has a large inversion on one of his chromosomes. How might this impact his offspring? -No impact because all genetic information is retained -Minor genetic abnormalities due to minimal deficiency in genetic material -Fewer autosomes because normal synapsis during meiosis does not occur -Severe phenotypic abnormalities caused by unbalanced chromatids
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Severe phenotypic abnormalities caused by unbalanced chromatids
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Crossing over within a pericentric inversion produces chromosomes that have extra copies of some genes and no copies of other genes. The fertilization of gametes containing these duplication or deficient chromosomes often results in children with syndromes characterized by developmental delay, mental retardation, abnormal development of organ systems, and early death. One study examined individual sperm cells of a male who was heterozygous for a pericentric inversion on chromosome 8 and determined that crossing over took place within the pericentric inversion in 26% of the meiotic divisions. Assume that a man and a woman are phenotypically normal, but the woman is heterozygous for a pericentric inversion on chromosome 8. The man is karyotypically normal. What is the probability that this couple's child will inherit a duplicated or deficient chromosome 8 that results from crossing over within this pericentric inversion?
answer
13 % Researchers determined that crossing over within this chromosome 8 pericentric inversion occurs in 26% of all meiotic events. When crossing over occurs during oogenesis in this heterozygous female, she will produce 50% recombinant and 50% nonrecombinant gametes. The probability of producing a gamete with a duplicated or deficient chromosome 8 is equal to the probability of crossing over within the pericentric conversion multiplied by the probability of inheriting a recombined chromosome.
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Familial Down syndrome is similar to primary Down syndrome in that it is caused by trisomy 21. However, in familial Down syndrome, all or part of the third copy of chromosome 21 has translocated onto another autosome, typically chromosome 14. In cases of familial Down syndrome, one of the parents of the affected child is often a carrier of a translocated chromosome. The translocation carrier parent does not have Down syndrome because he or she has a total of two copies of chromosome 21. Suppose that a woman is a translocation carrier of chromosome 21 on chromosome 14. She conceives six zygotes with a normal man who carries no aneuploidies. Match the description of the chromosomes inherited by each zygote with the viability of the zygote. A. Viable normal or translocation carrier
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2 normal copies of Chromosome 14 + 2 normal copies of Chromosome 21, 2 normal copies of Chromosome 14 + 1 normal copy of Chromosome 21 + 1 21 to 14 translocation
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Familial Down syndrome is similar to primary Down syndrome in that it is caused by trisomy 21. However, in familial Down syndrome, all or part of the third copy of chromosome 21 has translocated onto another autosome, typically chromosome 14. In cases of familial Down syndrome, one of the parents of the affected child is often a carrier of a translocated chromosome. The translocation carrier parent does not have Down syndrome because he or she has a total of two copies of chromosome 21. Suppose that a woman is a translocation carrier of chromosome 21 on chromosome 14. She conceives six zygotes with a normal man who carries no aneuploidies. Match the description of the chromosomes inherited by each zygote with the viability of the zygote. B. Viable with Downs Syndrome
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1 Normal copy of Chromosome 14 + 2 normal copies of Chromosome 21 + 1 21 to 14 translocation
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Familial Down syndrome is similar to primary Down syndrome in that it is caused by trisomy 21. However, in familial Down syndrome, all or part of the third copy of chromosome 21 has translocated onto another autosome, typically chromosome 14. In cases of familial Down syndrome, one of the parents of the affected child is often a carrier of a translocated chromosome. The translocation carrier parent does not have Down syndrome because he or she has a total of two copies of chromosome 21. Suppose that a woman is a translocation carrier of chromosome 21 on chromosome 14. She conceives six zygotes with a normal man who carries no aneuploidies. Match the description of the chromosomes inherited by each zygote with the viability of the zygote. C. Inviable
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1 normal copy of 14 + 2 normal copies of 21, 1 normal copy of 21 + 2 normal copies of 14 and 1 normal copy of 21 + two normal copies of 14 + 1 21 to 14 translocation
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About 0.3% of human live births are trisomic. In contrast, only 0.02% of human live births are monosomic. Select the best explanation for why the occurrence of monosomics is less than that of trisomics. -Meiotic nondisjunction rarely produces monosomic gametes. -Mitosis is less likely to be completed correctly in monosomics than in trisomics. -Deleterious recessive alleles are always expressed on the monosomic chromosome but not on the trisomic chromosomes. -Gene dosage imbalance is more likely to lead to spontaneous abortion in monosomics than in trisomics.
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Deleterious recessive alleles are always expressed on the monosomic chromosome but not on the trisomic chromosomes.
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Which of the following statements describe mosaicism? 1. An arm wrestler's right-arm muscles are larger than those on his left. 2. A tortoiseshell cat has patches of orange and black fur. 3. A cancerous tumor develops in a woman's ovary. 4. The skin on a person's face and arms becomes much darker than the skin on the rest of the body after a summer of working outdoors. 5. A child with the phenotypic features characteristic of Down syndrome has a mixture of normal cells and cells with three copies of chromosome 21.
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2,3 and 5
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In the fruit fly, Drosophila melanogaster, a known deletion on the X chromosome removes both a gene involved in the fly's development and the gene for eye color. The deletion is lethal when homozygous or hemizygous. Flies that are heterozygous for the mutation are viable, but have indentations at the wing margin. Therefore, the deletion is named the Notch mutation. The allele for wild type eyes is dominant over the allele for white eyes. Predict the phenotypic ratio of the offspring from a cross between a white-eyed notched female and a wild type male. -1 white-eyed notched female : 1 wild type female : 1 white-eyed notched male : 1 wild type male -1 wild type female : 1 notched female : 1 white-eyed male -1 white-eyed female : 1 notched female : 1 white-eyed male -1 wild type female : 1 notched female : 1 white-eyed male : 1 wild-typenotched male
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1 wild type female : 1 notched female : 1 white-eyed male
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Metacentric
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The centromere is located approximately in the middle, so the chromosome has 2 arms of equal length
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Submetacentric
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The centromere is displaced toward one end (On human chromosomes, the short arm is designated by a P and the long arm by the letter q)
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Acrocentric
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The centromere is near one end, producing a long arm and a knob or satellite at the other end
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Telocentric
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The centromere is at or very near the end of the chromosome
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Karyotype
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The complete set of chromosomes possessed by an organism
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What are the 3 different categories of Chromosome Mutation?
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Chromosome Rearrangements, Aneuploidy, Polyploidy
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Chromosome Rearrangement
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Alter the structure of chromosomes
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Aneuploidy
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The number of chromosomes is altered, added or deleted
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Polyploidy
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One or more complete sets of chromosomes are added
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What are the four basic types of chromosome rearrangements?
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Duplications, Deletions, Inversions and Translocations
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True/False Many rearrangements originate when double stranded breaks occur in DNA molecules found within a chromosome
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True
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True/False Double stranded breaks in DNA often cause death in cells
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True
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Chromosome Duplication
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is a mutation in which part of the chromosome has been doubled
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Tandem Duplication
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chromosome rearrangement on which a duplicated chromosome segment is adjacent to the original segment
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The following is an example of what type of Duplication: Normal: AB*CDEFG Mutation: AB*CDEFEFG
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Tandem Duplication
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Displaced Duplication
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Chromosome rearrangement in which the duplicated segment is some distance from the original segment, either on the same chromosome or on a different one.
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The Following is an example of what? Normal: AB*CDEFG Mutation: AB*CDEFGEF
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Displaced Duplication
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Reverse Duplication
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Duplication of a chromosome segment in which the sequence of the duplicated segment is inverted relative to the sequence of the original segment.
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The following is an example of what? Normal: AB*CDEFG Mutation: AB*CDEFFEG
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Reverse Duplication
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Segmental Duplication
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Duplicated chromosome segments larger than 1000 bp
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Most chromosomal duplication are what?
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Intrachromosomal Duplications, the 2 copies are found on the same chromosome'
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Duplications may have major effects on what?
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The phenotype
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Unequal Crossing Over
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misalignment of the two DNA molecules during crossing over, resulting in one DNA molecule with an insertion and the other with a deletion
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Unbalanced Gene Dosage
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The amount of a particular protein synthesized by a cell is often directly related to the number of copies of its corresponding gene
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Chromosomal Deletion
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The loss of a chromosome segment
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A large deletion can be easily detected because....
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the chromosome os noticeably shortened
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What happens if the deletion includes the centromere?
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The chromosome will not segregate in mitosis or meiosis and will usually be lost
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Many deletions are lethal because...
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All copies of any essential genes located in the deleted region are missing
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3 Reasons why deletions in Heterozygotes may have multiple effects on the individual
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1. The heterozygous condition may produce imbalances in the amounts of gene products similar to those produced by extra gene copies 2. Normally recessive mutations may be expressed when the wild type allele has been deleted 3. Some genes must be present in 2 copies for normal function
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Pseudodominance
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expression of a normally recessive allele owing to deletion on the homologous chromosome
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Haploinsufficient
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Gene that must be present in 2 copies for normal function. If one copy is missing a mutant phenotype is produced.
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Chromosome Inversion
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A segment of a chromosome has been inverted 180 degrees
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Paracentric inversions
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inversions that do not include the centromere
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Pericentric inversion
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inversions that include the centromere
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Position Effect
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dependence of the expression of a gene on the gene's location in the genome
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What happens with crossing over within an inversion
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the outcome is abnormal gametes that don't give rise to viable offspring, thus no progeny are observed.
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Dicentric Chromatid
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Chromatid that has 2 centromeres
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Acentric Chromatid
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Chromatid that lacks a centromere
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Dicentric and Acentric Chromatids are produced when crossing over takes place within a
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Paracentric Inversion
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Dicentric Bridge
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Structure produced when the two centromeres of a dicentric chromatid are pulled toward opposite poles, stretching the dicentric chromosome across the center of the nucleus.
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What happens in a Pericentric Inversion
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No dicentric/acentric bridges, some chromosomes have too many copies of some genes and no copies in others.
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Translocations
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1. Movement of a chromosome segment to a nonhomologous chromosome or to a region within the same chromosome 2. Movement of a ribosome along mRNA in the course of translation
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Nonreciprocal Translocation
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Movement of a chromosome segment to a nonhomologous chromosome without any reciprocal exchange of segments
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Reciprocal Translocation
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Reciprocal exchange of segments between two nonhomologous chromosomes
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True of False: All chromosomes of the same species would have the same centromeric positions
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True
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The spread of a complete metaphase chromosome set presented for diagnostic purposes is called a ______.
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Karyotype
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Failure to separate for homologous chromosomes or sister chromatids is referred to as _______.
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Nondisjunction
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Of all cases of primary Down syndrome, 92% is caused by _______.
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Trisomy
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Robertsonian Translocation
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Translocation in which the long arms of two acrocentric chromosomes become joined to a common centromere, resulting in a chromosome with two long arms and usually another chromosome with two short arms.
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alternate segregation
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Type of segregation that takes place in a heterozygote for a translocation. If the original, nontranslocated chromosomes are N1 and N2 and the chromosomes containing the translocated segments are T1 and T2, then alternate segregation takes place when N1 and N2 move toward one pole and T1 and T2 move toward the opposite pole.
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adjacent-1 segregation
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Type of segregation that takes place in a heterozygote for a translocation. If the original, nontranslocated chromosomes are N1 and N2 and the chromosomes containing the translocated segments are T1 and T2, then adjacent-1 segregation takes place when N1 and T2 move toward one pole and T1 and N2 move toward the opposite pole.
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adjacent-2 segregation
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Type of segregation that takes place in a heterozygote for a translocation. If the original, nontranslocated chromosomes are N1 and N2 and the chromosomes containing the translocated segments are T1 and T2, then adjacent-2 segregation takes place when N1 and T1 move toward one pole and T2 and N2 move toward the opposite pole.
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What happens in translocations?
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In translocations, parts of chromosomes move to other nonhomologous chromosomes or to other regions of the same chromosome.
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How can translocations affect the phenotype?
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Translocations can affect the phenotype by causing genes to move to new locations, where they come under the influence of new regulatory sequences, or by breaking genes and disrupting their function
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Fragile Sites
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Constriction or gap that appears at a particular location on a chromosome when cells are cultured under special conditions.
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fragile-X syndrome
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A form of X-linked intellectual disability that appears primarily in males; associated with a fragile site that results from an expanding trinucleotide repeat.
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True or False? Common fragile sites are present in all humans and are a normal feature of chromosomes. Common fragile sites are often the locations of chromosome breakage and rearrangements in cancer cells, leading to chromosome deletions, translocations, and other chromosome rearrangements
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True
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Copy-Number Variations
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Difference among individual organisms in the number of copies of any large DNA sequence (larger than 1000 bp).
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structural variants
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Collective term for chromosome rearrangements and copy-number variations.
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Aneuploidy
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Change from the wild type in the number of individual chromosomes; most often an increase or decrease of one or two chromosomes.
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Polyploidy
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Possession of more than two sets of chromosomes.
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In what ways can Aneuploidy arise?
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1. A chromosome may be lost in the course of mitosis or meiosis if, for example, its centromere is deleted 2. The small chromosome generated by a Robertsonian translocation may be lost in mitosis or meiosis 3. Nondisjunction, the failure of homologous chromosomes or sister chromatids to separate in meiosis or mitosis
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Nullisomy
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Absence of both chromosomes of a homologous pair (2 n - 2).
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Monosomy
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is the loss of a single chromosome, represented as 2n - 1. A human monosomic zygote has 45 chromosomes.
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Trisomy
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is the gain of a single chromosome, represented as 2n + 1. A human trisomic zygote has 47 chromosomes. The gain of a chromosome means that there are three homologous copies of one chromosome. Most cases of Down syndrome, discussed later in this section, result from trisomy of chromosome 21.
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Tetrasomy
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is the gain of two homologous chromosomes, represented as 2n + 2. A human tetrasomic zygote has 48 chromosomes. Tetrasomy is not the gain of any two extra chromosomes, but rather the gain of two homologous chromosomes, so that there are four homologous copies of a particular chromosome.
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Double Trisomic
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An individual that has an extra copy of each of two different (nonhomologous) chromosomes. 2n+1+1
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How does aneuploidy affect the phenotype?
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Aneuploidy usually alters the phenotype drastically. In most animals and many plants, aneuploidies are lethal. Because aneuploidy affects the number of gene copies, but not their nucleotide sequences, the effects of aneuploidy are most likely due to abnormal gene dosage.
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How does aneuploidy affect humans?
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Aneuploidy in humans usually produces such serious developmental problems that spontaneous abortion results. Only about 2% of all fetuses with a chromosome mutation survive to birth.
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Down Syndrome
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Human condition characterized by variable degrees of intellectual disability, characteristic facial features, some retardation of growth and development, and an increased incidence of heart defects, leukemia, and other abnormalities; caused by the duplication of all or part of chromosome 21.
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Primary Down Syndrome
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Human condition caused by the presence of three copies of chromosome 21.
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Familial Down Syndrome
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Human condition caused by a Robertsonian translocation in which the long arm of chromosome 21 is translocated to another chromosome; tends to run in families.
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Translocations Carriers
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Individual organism heterozygous for a chromosome translocation.
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Uniparental Disomy
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Inheritance of both chromosomes of a homologous pair from a single parent.
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genetic mosaicism
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Condition in which regions of tissue within a single individual have different chromosome constitutions.
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gynandromorphs
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Individual organism that is a genetic mosaic for the sex chromosomes, possessing tissues with different sex-chromosome constitutions.
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autopolyploidy
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Condition in which all the sets of chromosomes of a polyploid individual are derived from a single species.
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allopolyploidy
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Condition in which the sets of chromosomes of a polyploid individual are derived from two or more species.
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unbalanced gametes
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Gamete that has a variable number of chromosomes; some chromosomes may be missing and others may be present in more than one copy.
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What causes Autopolyploidy
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Autopolyploidy is caused by accidents of mitosis or meiosis that produce extra sets of chromosomes, all derived from a single species.
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True or False? Problems in chromosome pairing and segregation often lead to sterility in autopolyploids, but many allopolyploids are fertile.
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True
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definition of euploidy
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a complete chromosome set or an exact multiple of the haploid chromosome set
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Haploid
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a single unpaired copy of each chromosome
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Monosomic
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Only one copy of a specific chromosome
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A man has a large inversion on one of his chromosomes. How might this impact his offspring?
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miscarriage or stillbirth caused by defective chromatids
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Many errors can occur during meiosis. What term describes the process of sister chromatids not separating at the centromere during cell division?
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nondisjunction
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Cytogenetics
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the study of inheritance and aberrations of heredity at the level of the chomosomes
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What does nondisjunction in meiosis 1 produce
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it produces 50% trisomic gametes and 50% monosomic gametes
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What does nondisjunction in meiosis 2 produce
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25% of gametes are trisomic 50% are normal 25% monosomic
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What has gene dosage compensation, and what does not?
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X-chromosome has gene dosage compensation but autosomes do not
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What is a meiotic consequence of trisomy?
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6 possible arrangements of chromosomes
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How does polyploidy arise?
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Due to catastrophic failure of cell division (spindle doesn't work, cytokinesis fails)
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True/False Odd numbers of n (1,3,5) are usually sterile
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True
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What is the significance of polyploidy?
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-increase in cell size -larger plant attributes -evolution: may give rise to new species
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What causes breaks in chromosomes that are induced by environmental agents?
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ionizing radiation heat viruses chemicals
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What causes breaks in chromosomes that are induced by genetic instability?
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Transposable genetic elements (transposons) error in crossing over chromosome sequence instability
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What is the cause of Prader-Willi Syndrome? What are the symptoms?
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heterozygous loss of part of 15q poor eating early in life then compulsive eating later developmental & behavioral problems mental retardation
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Cytologically duplication of genes......
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can lead to gene families with new functions arising (globin family)
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Consequences of a crossover in the inversion loop of a paracentric inversion chromosome:
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1 normal chromosome 1 dicentric chromosome 1 acentric fragment 1 inversion chromosome
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The position effect
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is seen in inversions and translocations and sometimes in deletions by new adjacencies of genes
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Fragile X Syndrome
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-the second leading cause of genetic intellectual disability (ID) -most common heritable form of ID -Males are affected; dominant in females but has low penetrance
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What are the general rules for Deletions?
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-Unpaired regions of homologs in meiosis 1 will loop out -reversion to wild-type does not occur -pseudodominance -lethality: essential genes and large deletions
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What are the general rules for Duplications?
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-unpaired regions of homologs in meiosis 1 will loop out -potential for unequal crossovers, leading to additional copies of regions -dosage effects can lead to a new phenotype duplicate genes provide material for new gene functions
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What are the general rules for Inversions?
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-linkage relationships are altered -break points can disrupt genes -Gametes are usually viable when: --no crossovers --crossover is outside inversion -Gamete viability is reduced when crossover is within the inversion loop -possible position effect
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What are the general rules for Translocations?
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-homozygotes have viable gametes -heterozygoes have reduced viability 50% -breakpoints can disrupt genes -possible position effect
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Additional copies of a gene _____ cause cellular problems.
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sometimes
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Which of the following terms correctly describes the eukaryotic chromosome figure presented on the right based on the centromere position?
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acrocentric
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The spread of a complete metaphase chromosome set presented for diagnostic purposes is called a
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karyotype
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Failure to separate for homologous chromosomes or sister chromatids is referred to as
answer
nondisjunction
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Of all cases of primary Down syndrome, 92% is caused by
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trisomy
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_______ is a type of polyploidy that arises from the hybridization between two different species
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allopolyploidy
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Which of the following statements about chromosome inversions is correct?
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Chromosome inversions flip a segment of a chromosome 180 degrees
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which of the following statements about chromosome translocation is correct?
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translocation can affect gene expression by moving a gene under the control of a different promoter
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What does diagram A in figure 8.3 represent??
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chromosome duplication
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What does diagram B in figure 8.3 represent?
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aneuploidy
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What does diagram C in figure 8.3 represent?
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polyploidy
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Which of the following statements about aneuploidy is true?
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One form of aneuploidy is a loss of both members of a homologous pair of chromosomes
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Which of the following statements of polyploidy is not true
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polyploidy is possible only between the members of the same species
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Which of the following statements about Down syndrome is true?
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Trisomy of chromosome 21 is well tolerated enough to give ruse to fully developed individuals
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During meiosis, errors occur during chromosome replication. Which term describes the rearranging of genetic material between nonhomologous chromosomes without a net loss or gain of genetic material
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translocation
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select the definition of aneuploidy
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the addition or loss of less than a full set of chromosomes or chromosome pair
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The following is a representation of a human karyotype, What type of genetic disorder is shown in this karyotype?
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trisomy
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Some people with turners syndrome are 45,X/46,XY mosaics. How could this mosaicism arise
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a cell loses a Y chromosome soon after fertilization in an XY embryo
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What did Griffith discover with his experiements?
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the transforming principle in bacteria
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In avery, macleod, and mccarty's experiements, homogenates from heat killed bacteria were treated with different enzymes, and the the ability of those homogenates to transform bacteria was assayed. Under which condition would transformation not occur?
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treatmeant with DNase
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In the hershey-chase experiment, DNA was demonstrated to be the genetic material because the 32p label for DNA localized to
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the bacterial pellet
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The major contribution of Franklin and Wilkins to the study of DNA was
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an x ray diffraction pattern
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THe sugar in DNA is called deoxyribose because it
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is missing a 2'-OH group
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A strong covalent bond between adjacent nucleotides is a
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phosphodiester bond
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The number of hydrogen bonds between complementary G-C pairs is
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3
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a left handed form of DNA is the
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Z-DNA
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A structure formed by a single-stranded DNA or RNA molecule that has complementary sequences is a
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hairpin
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Which of the following descriptions about prokaryotic versus eukaryotic DNA replication is not correct?
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in prokaryotes, the DNA replication is unidirectional; in eukaryotes, the replication is bidirectional
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Which of the following statements describes the semiconservative model of FNA replication correctly?
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if proposes that the two nucleotide strands unwind and each serves as a template for a new DNA molecule
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Which of the following statements describes the conservative model of DNA replication correctly
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it proposes that the entire double stranded DNA molecule serves as a template for a whole new molecules of DNA
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What property of the DNA molecule explains the necessity for Okazaki fragments
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DNA is antiparallel
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Which of the following components required for prokaryotic DNA replication is not involved in unwinding the DNA template
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DNA ligase
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Which enzyme is responsible for the replication of chromosome ends in germ cells and certain proliferating somatic cells
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telomerase
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Which of the following statements about RNA is not true
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RNA is a more stable molecule than DNA
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Which of the following classes of RNA serves as the coding instruction read by the ribosome to produce a polypeptide chain
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mRNA
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The diagram below represents a transcription unit comprised of three critical regions, the promoter, the coding region, and the terminator. Which region would not be present in the final RNA transcript?
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promoter
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Most bacterial RNA polymerases are made up of five subunits that have distinct functions for transcription. Which of the following subunits does not permanently associate with the enzyme core?
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sigma
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Whereas bacterial cells typically possess only one type of RNA polymerase, most eukaryotic cells possess ________ distinct types of RNA polymerase.
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3
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Frequently, important DNA regions with specific functions tend to contain short stretches of nucleotides that are conserved across different organisms and are recognized by specific proteins. What are these conserved sequences called?
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consensus sequences
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How is the transcription start site determined in bacteria?
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by the binding of RNA polymerase to the consensus sequences of the promoter
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in eukaryotic cells, promoter consensus sequnces are recoginzed by accessory proteins that recruit a specific RNA polymerase. Whihc of the following types of accessory proteins serve this purpose?
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general transcription factors
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which of the following contains the TATA-binding protein TBP
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transcription factor TFIID
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How would the deletion of the Shine-Dalgamo sequence affect a bacterial mRNA?
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translocation would not occur
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Proteins are composed of _______ linked together by _______ bonds.
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amino acids; peptide
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The way that proteins fold into beta pleated sheets and alpha helicies is dependent on their
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primary structure
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Which of the following is not involved in the initiation of translocation in bacteria
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tRNA carrying the next amino acid that will occupy the A site
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Which of the following is the first step of translocation elongation?
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a charged tRNA binds to the A site
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When mRNAs are being translated simultaneously by multiple ribosomes, the structure is known as a
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polyribosome
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Which of the following is not true regarding cancer cells?
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cancer cells respond to normal cell cycle controls but proliferate at an abnormal rate
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Which of the following statements best describes the clonal evolution of tumors
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tumor cells acquire more somatic mutations that allow them to become increasingly more aggressive in their proliferative properties
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Which of the following statements best describes Alfred Knudson's two-hit hypothesis?
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retinoblastoma results from two separate genetic defects, both of which are necessary for cancer to develop
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Mutant versions of genes that are normally involved in driving the cell cycle are known as
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oncogenes
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Genes that normally produce factor that inhibit cell division are called
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tumor suppressor genes
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tumor-supressor genes typically cat in a _______ manner, and oncogenes typically act in a _______ manner
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recessive; dominant
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How might a mutation in a gene that regulates telomerase lead to cancer
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the mutation could allow telomerase to be expressed when it should not be
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Which of the following is not a way in which chromosome mutations could lead to cancer?
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Translocation of a tumor suppressor gene to a new location puts it under the control of a strong promoter
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What contribution did James Watson and Francis Crick make to our understanding of DNA
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they pieced together the available evidence and modeled the structure of DNA
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What is the key feature of DNA that allows it to be copied?
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complementary base pairing
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During meiosis, errors occur during chromosome replication. Which term describes the rearranging of genetic material between nonhomologous chromosomes without a net loss or gain of genetic material
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translocation
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Triploid
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three homologues of each chromosome
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trisomic
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one extra copy of a specific chromosome
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n=3
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a genome composed of three unique chromosomes
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select the definition of polyploidy
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a chromosomal complement with at least three complete sets of homologous chromosomes
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the following is a representation of a human karyotype. What type of genetic disorder is shown in this karyotype?
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trisomy
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select the statements that explain why duplication is a driving force for evolution and the generation of new genes
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duplicated genes provide extra copies of DNA tat are not constrained by an essential function phenotypic cariations can occur when random fixed mutations are introducted into a new chromosomal environment genes duplicate and then diverage from the original sequence to create multigene families
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select the statements that describe the effect of copy number variation on human phenotypes
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oncogene over expression due to a gain in copy number can cause cancer increase in the copy number of genes involved in starch digestion allows for a high starch diet copy number variations are associated with complex disorders such as autism
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Which of the following describe mosaicism
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a child with the phenotypic features characteristic of down syndrome has a mixture of normal cells and cells with three copies of chromosome 21 a tortoiseshell cat has patches of orange and black fur a cancerous tumor develops in a smokers lung
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select each of the characteristics that are key features of genetic material
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it must be able to replicate and transmit to progeny it must periodically mutate to generate variation it must encode the blueprint to form proteins and other structures
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which of the following relations will be found in the percentages of bases of a double stranded DNA molecule
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a/t=g/c a+g=c+t (a+g)/(C+t) = 1.0
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james watson and drancis crick used the x-ray diffraction image taken by Rosalind Franklin to deduce structural properties of B-form DNA. What findings did Watson and Crick make from this image?
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includes 10 base pairs per repeat has a consistent diameter shaped like a helix
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What is the key feature of DNA that allows it to be copied
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complementary base pairing
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Which of the following statements describes purines and pyrimidines in DNA molecules
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pyrimidines form hydrogen bonds with purines pyrimidines consist of a one ring structure
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identify the key structural features of a DNA molecule
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the backbone of DNA is made of a sugar and a phosphate molecule DNA bases are always paired using Watson Crick base pairing DNA strands are antiparallel and include a 5' end and a 3' end
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mRNA
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contains the codons for the polypeptide sequence
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rRNA
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catalyzes peptide bond formation
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tRNA
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hydrogen bonds with codon, transports amino acids to the ribosome
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Identify the statements that are features of a promoter
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in both prokaryoties and eukaryotes, the promoter is located in the 5' direction, upstream from the transcription start site in eukaryotes, the promoter often contains a TATA box which is where the TATA binding protein binds in prokaryotes the promoter contains a -35 and -10 region upstream of the transcription start site
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which of the following statements describes the function of the sigma factor in prokaryotic transcription
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it facillitates the binding of RNA polymerase to the promoter to initiate transcription
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according to the centra dogma, double-stranded DNA serves as the template for the production of RNA during transcription. Which of the two DNA strands serves as the template for transcription
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either DNA strand may be used as a template by RNA polymerase, but a single DNA strand oriented in the 3'-5' direction is used as a template each time transcription occurs
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What is the role of the eukaryotic promoter in transcription
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the site where RNA polymerase binds to initiate transcription
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transcription
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acts on only one strand catalyzed by RNA polymerase localized in the cytoplasm in prokaryotic cells
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Replication
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catalyzed by DNA polymerase a primer is required localized in the cytoplasm in prokaryotic cells
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What happens during the termination step of DNA transcription
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the mRNA detaches from the RNA polymerase as the RNA polymerase leaves the DNA strand
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What happens during the elongation step of DNA transcription
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RNA polymerase moves along the template strand of the DNA creating an mRNA strand
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How would the deletion of the Shine-Dalgamo sequence affect a bacterial mRNA?
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translocation would not occur
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The example below shows the splicing of a hypothetical premature mRNA transcribed from the gene for yellow flourescent protein. Two different YFP mRNAs isofrom A and isoform B are produced by alternative splicing. What are the possible outcomes of the alternative splicing shown?
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the protein translated from isoform B is stable but lacks a functional domain the protein translated from isoform A mRNA possesses an additional functional domain isoform-A mRNA is degraded faster than isoform-B mRNA is
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Why is a cap added to mRNA but not to tRNA or rRNA
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RNA polymerase II transcribes mRNA, whereas RNA polymerase I transcribes rRNA, and RNA polymerase III transcribes tRNA. The domain that assists other enzymes in adding the cap is found in RNA polymerase II only
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What is the function of the spliceosome?
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the spliceosome produces a mature mRNA by connecting teo exons and releasing the intron
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Which description applies to alternative mRNA splicing?
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processing of exons in mRNA that results in a single gene coding for multiple proteins
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Use the diagram provided to select the correct statement regarding RNA splicing
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only coding exons are spliced together to make finished mRNA
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Why can alternative splicing of messenger RNAs be advantageous for eukaryotic organisms?
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increases he variety of proteins that can be produced
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How do the nucleus and ribosomes work together to generate a protein?
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in the nucleus, DNA is transcribed to mRNA which the ribosomes use as instructions to synthesize a specific protein
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which part is responsible for the unique properties of each amino acid?
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R group
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What is the sequence of the anticodon from the 3' to 5' end of the tRNA in the A site
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UGC
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What is the next amino acid added to the growing polypeptide chain?
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Thr
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Which of the following events occur during eukaryotic translocation termination
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A protein recognizes the stop codon and the ribosome dissociates from the mRNA
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In general, what causes normal cells to become cancer cells
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loss of cell cycle control
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Cancer is a genetic disorder. How does cancer differ from most other genetic disorders?
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Most genetic disorders are inherited through germ cells from parents. Most cancers are, to some extent, the result of mutations in somatic cells that occur during an organism's lifetime
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Suppose Alia recently learned that she inherited a mutant BRCA1 allele from her mother, who had breast cancer. BRCA1 is a tumor suppressor gene that is related to breast cancer. Why would Alia be at a higher risk for getting breast cancer at an earlier age than her sister, Tiffany, who inherited a normal BRCA1 allele from their mother
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Someone with one mutant allele in a tumor suppressor gene only requires a mutation in the one remaining normal allele for tumors to form
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Which of the following mutations have the potential to cause cancer
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a loss of function mutation in a tumor suppressor gene a gain of function mutation in a proto-oncgene
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Select the statements that accurately describe different ways that translocations could lead to cancer
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a new sequence is added to a proto-oncogene. the modified gene now produces a new protein that increases the rate of cell division a gene for a protein that is involved in a mitotic checkpoint that is placed next to the regulartory sequnce of a different gene. the gene is now expressed at innapropriate times a translocation disrupts the sequence of a gene for a tumor-suppressor protein. the resulting protein cannot function properly
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How do viruses contribute to cancer
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by driving overexpression of a cellular proto-oncogene by inactivating tumor suppressor genes
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select the viruses that can cause human cancer
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hepatitis C epstein barr virus human papillomavirus