What is the definition of cross-fertilization?
- mating two heterozygous plants to produce offspring
- mating two plants with different alleles to produce offspring
- mating two plants with different genes to produce offspring
- mating two plants to produce offspring
answer
mating two plants to produce offspring
Cross-fertilization just means that offspring are the result of two parents. Self-fertilization is the opposite.
Specific genotypes are not involved in this definition.
question
Which of the following is true about dominant alleles?
- Dominant alleles mask the presence of recessive alleles.
- Dominant alleles are passed on more often than recessive alleles.
- Dominant alleles are more important than recessive alleles.
- Dominant alleles are more common in the population than recessive alleles.
- Dominant alleles are healthier than recessive alleles.
answer
Dominant alleles mask the presence of recessive alleles.
Dominance has nothing to do with how frequent the allele is and all alleles have a 50/50 chance of being passed on to each offspring.
question
What is a gene made of?
- proteins
- alleles
- nucleotides
- chromosomes
- traits
answer
A gene is a string of nucleotides.
question
What feature controls the tightness of the linkage of two genes?
- the distance between the two chromosomes during meiosis
- the importance of the genes in a metabolic pathway
- the distance between the two genes
- whether both genes are dominant or recessive
- the length of the two genes
answer
the distance between the two genes
Genes that are close to each other on the same chromosome are more closely linked than genes that are far apart.
question
During which phase of the cell cycle does the law of independent assortment occur?
- anaphase II
- anaphase I
- metaphase II
- metaphase I
- anaphase
- metaphase
answer
anaphase I
Chromosomes separate during anaphase I. During anaphase II, the chromosomes that separate are sister chromatids and often identical.
question
Considering pea flowers, where purple is dominant to white, describe the genotype of a white flower.
- purple
- homozygous recessive
- PP
- Pp
- white
- heterozygous recessive
answer
homozygous recessive
You could also write "pp" to show this genotype.
question
A mother has two X chromosomes. A father has an X and a Y. What are the odds that they produce a female child?
- 75%
- 50%
- 100%
- 25%
answer
50%
Because the father passes an X and a Y at equal frequency, that results in only half of the offspring having XX.
question
Considering pea flowers, where purple is dominant to white, describe the genotype of a plant with the alleles Pp.
- purple
- heterozygous
- heterozygous dominant recessive
- homozygous
- homozygous dominant
- white
answer
heterozygous
A heterozygote is a plant with two different alleles.
question
Which of the following is most likely to be passed on to the next generation?
- a mutation that caused breast cancer
- a mutation resulting from too many sun burns
- a mutation in the DNA in cells in the testicles
- increased muscle mass resulting from exercise
- blindness from drinking methanol
answer
a mutation in the DNA in cells in the testicles
These produce sperm cells by meiosis. If the DNA of the testicles is mutated, the sperm will be mutated as well.
question
What is a test cross?
- crossing two pure-breeding organisms of opposite phenotype
- crossing two organisms heterozygous for a trait
- crossing an organism with a dominant phenotype with one that has a recessive phenotype
- crossing a heterozygous organism with one that has a recessive phenotype
- crossing two organisms with the dominant phenotype
answer
crossing an organism with a dominant phenotype with one that has a recessive phenotype
This is the easiest way to determine if the organism with the dominant phenotype is homozygous or heterozygous.
question
Mendel worked _____.
- on gene mapping
- with fruit flies
- on problems involving characters that were inherited together more often than expected by chance
- on the Human Genome Project
- in a monastery
answer
Mendel was a monk who worked in his monastery garden.
question
Which of the following represents an exception to the law of independent assortment?
- incomplete dominance
- linkage
- nondisjunction
- haploid
- multiple alleles
answer
linkage
Linked genes do not assort independently.
question
A gene is moved from chromosome 12 to chromosome 15. What has happened to this gene?
- The gene has a new mutation.
- This is a new chromosome.
- This is a new gene.
- The gene is in a new locus.
- The gene has a new allele.
answer
The gene is in a new locus.
Changing the position of a gene changes the locus of the gene.
question
In the 1800s, it was commonly believed that the traits of both parents for any feature blended to create the offspring and that the blended trait was passed on. Which of the following observations was most important to Mendel's understanding of genes as unchanged units of information?
- Recessive traits reemerge in later generations.
- Pure breeding lines always produce the same offspring.
- Recessive traits are not expressed in children.
- Dominant traits are more likely to be inherited than recessive traits.
- Dominant traits are always expressed in children.
- Dominant traits are more common in the population.
answer
Recessive traits reemerge in later generations.
A blended trait could not reemerge unchanged as a parental trait in the blending model.
question
Which of these facts, if he had known them, might have lead Mendel to formulate different rules for inheritance?
- There are many genes on each chromosome.
- Alleles of the same gene are separated during anaphase I.
- Genes are made of DNA.
- DNA is duplicated during S phase.
- Alleles of the same gene are contained on homologous chromosomes.
answer
There are many genes on each chromosome.
Mendel may have modified his rule of independent assortment if he had known this.
question
A pea plant with purple flowers is crossed with a pea plant with white flowers. One-half of the offspring have purple flowers and one-half have white flowers. What are the genotypes of the parent plants?
- pp x pp
- PP x pp
- Pp x Pp
- Pp x pp
answer
Pp x pp
The white plant is automatically recessive and the purple plant must have a recessive allele if any offspring have white flowers. This is also called a test cross.
question
Two healthy parents give birth to a child with cystic fibrosis, a recessive disorder. What can we say about both parents?
- One parent must be heterozygous for the disease allele. The other must be homozygous healthy.
- Both parents are homozygous for the disease allele.
- One parent must be heterozygous for the disease allele.
- One parent must be homozygous for the disease allele.
- Both parents are heterozygous for the disease allele.
answer
Both parents are heterozygous for the disease allele.
Both parents must carry the recessive allele for the child to have received two recessive copies.
question
A person is heterozygous for hair texture. Which of these statements is correct about this person's DNA?
- This person has two different homologues for hair texture.
- This person has two different genes for hair texture.
- This person has two different alleles at the loci for hair texture.
- This person has the same allele at the loci for hair texture.
- This person has the same homologues for hair texture.
- This person has two of the same gene for hair texture.
answer
This person has two different alleles at the loci for hair texture.
Heterozygotes for a particular trait carry two different alleles.
question
A purple-flowered pea plant self-fertilizes and produces both purple and white offspring. What is its genotype?
- Pp x PP
- Pp x Pp
- Pp
- PP
- Pp x pp
- pp
answer
Pp
This is similar to the F1 cross described in Mendel's work.
question
During which phase of the cell cycle does the Law of Segregation of Alleles occur?
- anaphase
- metaphase II
- anaphase II
- anaphase I
- metaphase I
- metaphase
answer
anaphase I
Homologues separate during anaphase I.
question
Genes provide the information needed to produce _____ in the cell.
- ribosomes
- lipids
- enzymes
- glucose
answer
enzymes
Genes produce proteins which can be enzymes.
question
How many enzymes are typically produced from a single gene?
- two
- one
- an unlimited number
- three
answer
one
question
How do mutations affect an organism?
- they may cause the development of a disease-causing allele
- they may cause the development of a more beneficial allele
- they, in some cases, may have no noticeable affect
- all of the above
answer
All of the above answers are correct.
question
DNA replication occurs at an unbelievably fast rate. Once replication is complete, we can expect to find a _____ number of mistakes.
- large
- small
- average
answer
small
DNA polymerase makes few mistakes.
question
A female that is planning to become pregnant is concerned about her exposure to environmental mutagens which may have caused DNA mutations. In order for these mutations to become heritable, they must affect the:
- her egg cells
- somatic cells
- all of her cells
answer
her egg cells
question
Which of the following would indicate a base pairing mutation in DNA?
- an A paired with a T
- a C paired with a G
- a G paired with a T
- all of the above are improper base pairs
answer
a G paired with a T
question
What are the possible genotypes of a person with type O blood?
- Ao, Bo
- oo
- Ao, Bo, oo
- Oo, oo
answer
oo
There is only one genotype that can result in the recessive phenotype, even in co-dominance.
question
Which of the following tools is never necessary when evaluating a gene with incomplete dominant inheritance?
- test cross
- genotypes
- phenotypes
- Punnett square
answer
test cross
A test cross is specifically used to determine if an individual with the dominant phenotype is a homozygote or a heterozygote. Genes that show incomplete dominance have a different phenotype for the heterozygote, so this test is unnecessary.
question
Why can't a color-blind father pass this condition on to his sons?
- The father only gives his Y chromosome to his sons.
- Children can only receive the color-blind allele from their mother.
- The father only gives his X chromosome to his sons.
- Fathers only pass on dominant alleles for color vision to their sons.
answer
The father only gives his Y chromosome to his sons.
The gene for color vision is contained on the X chromosome, which the father never gives to his sons.
question
What type of inheritance is responsible for creating Jacob syndrome?
- recessive
- trisomy 21
- sex-linked
- incomplete dominant
- nondisjunction
- dominant
answer
This is a nondisjunction disorder where the male has an extra Y chromosome.
question
A pure-breeding plant with red flowers is crossed with a pure-breeding plant with white flowers. The offspring all have pink flowers. What type of inheritance is involved here?
- multi-gene phenotype
- multi-allele gene
- co-dominance
- pleiotropic gene
- incomplete dominance
answer
incomplete dominance
Here the heterozygote has its own phenotype, halfway between both parental phenotypes.
question
In studying the karyotypes of a random sample of 10,000 people, you find the following disorders related to nondisjunction of chromosomes: 11 people have trisomy 21 3 women have XO 10 men have XXY 9 women have trisomy X 11 men have XYY You find no other cases of extra or missing chromosomes. What might you conclude about nondisjunction disorders in general?
- Extra or missing copies of most of the chromosomes must be lethal early in life.
- Nondisjunction of chromosome 21 must be directly related to the age of the mother.
- An XY homologue pair must be extremely susceptible to nondisjunction.
- Extra or missing copies of most of the chromosomes must cause no symptoms.
answer
Extra or missing copies of most of the chromosomes must be lethal early in life.
- For every chromosome other than 21 and the sex chromosomes, having an extra or missing copy is lethal, usually before birth. That is why no examples of these nondisjunctions are in your sample population.
question
Considering all the genetic diseases covered in this chapter, what general conclusion can you draw about genetic diseases?
- Most genetic diseases are pleiotropic.
- Most genetic diseases are eventually lethal.
- Most genetic diseases show incomplete dominance.
- Most genetic diseases follow the rules of Mendelian genetics.
- Most genetic diseases are the result of multi-gene phenotypes.
answer
Most genetic diseases are pleiotropic.
- Very few diseases have just one symptom. The human body uses the same genes in multiple organs, so multiple organs are affected by any one mutation.
question
Considering the information you have read about cystic fibrosis, which of the following descriptions of the disease best applies?
- Cystic fibrosis is a recessive disease with pleiotropic effects.
- Cystic fibrosis is a co-dominant disease.
- Cystic fibrosis is an incomplete dominant disease with a heterozygote phenotype.
- Cystic fibrosis is a multi-gene disorder with pleiotropic effects.
- Cystic fibrosis is a dominant disease with minimal effects.
answer
Cystic fibrosis is a recessive disease with pleiotropic effects.
- Though the disorder involves only one gene with a recessive allele, the symptoms range from respiratory to digestive to reproductive.
question
Why do males suffer from sex-linked disorders more often than females?
- Males can express single recessive alleles from their single Y chromosome.
- Males can express single recessive alleles from their single X chromosome.
- Fathers are more likely to pass disease alleles on to sons than to daughters.
- The diseases that are sex-linked require the expression of testosterone.
- The disease genes are only located on the Y chromosome of males.
answer
Males can express single recessive alleles from their single X chromosome.
- A female would require two recessive alleles for any gene in order to express the recessive allele.
question
Consider a disease allele that is both dominant and lethal to patients that possess it. How could such an allele be passed on from generation to generation?
- The disease must leave a small percentage of patients alive, so that some can pass it on to their children.
- There must be a medical treatment to sustain life, allowing the patients to reproduce.
- The disease must be lethal later in life, after the patient has had children.
- The disease must be sex-linked, so that women can be carriers.
- The disease must skip generations, like diabetes or albinism.
answer
The disease must be lethal later in life, after the patient has had children.
- All dominant lethal disorders, by definition, must strike after childbearing years. If the disorder was lethal to infants, it would never be passed on, as there could be no healthy carriers with a dominant disorder.
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