Genetics Final Exam Mastering Questions

2 September 2022
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question
The role of the primers in PCR is _______. A. to define the target region and provide a 3' end that can be extended by taq polymerase B. solely to define the target region C. to denature the template DNA and define the target region D. the annealing temperature is maintained until polymerase has finished extension of the new strands
answer
A Primers bind to end of the target DNA strands, then taq polymerase synthesizes a new strand using the target DNA as a template.
question
If there are five molecules of DNA containing the target region at the beginning of a PCR reaction, how many copies of the target will be present after three rounds of amplification? A. 500 B. 15 C. 125 D. 40
answer
D Correct. The number of target sequences is doubled with each replication cycle.
question
Immediately after the primers have annealed to the target sequence, _______. A. the temperature is raised to cause denaturation B. the temperature is lowered so that taq polymerase can extend the primers C. the temperature is raised so that taq polymerase can extend the primers D. the annealing temperature is maintained until polymerase has finished extension of the new strands
answer
C Correct. The temperature is raised to 70-75∘C, the temperature over which taq polymerase is optimally active.
question
Which of the following molecules is not required for a PCR reaction? A. Primer B. DNA C. DNTPs D. Ligase
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D Ligase is not required for a PCR reaction. The enzyme used during PCR is a thermostable DNA polymerase.
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The thermostability of Taq polymerase is required during the annealing phase of PCR. A. True B. False
answer
B The annealing phase takes place at the lowest temperature of PCR. Taq polymerase is derived from bacteria that live in hot springs, so the enzyme is thermostable, meaning that its enzymatic properties can withstand the high temperatures needed for denaturation.
question
What is the purpose of raising the temperature to 90-95°C at the beginning of each cycle of PCR? A. To renature two single DNA strands B. To extend the primer C. To attach the primer D. To separate the double‑stranded DNA
answer
D The temperature is raised to denature the double‑stranded DNA molecule into single strands.
question
What is the function of restriction endonucleases in bacteria? A. They serve no function. B. They provide a defense mechanism against infection by viruses. C. They allow bacteria to genetically recombine with other bacteria. D. They allow bacteria to engineer new DNA fragments.
answer
B Restriction endonucleases recognize and degrade viral DNA, thus preventing viral infections
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Restriction endonucleases cut DNA at specific recognition sequences and then bond two strands covalently with the same "sticky ends." A. True B. False
answer
B Restriction endonucleases cut DNA at specific sequences, but DNA ligase must be used to bond two strands covalently with the same "sticky ends."
question
BamHI cuts the sequence 5′ G|GATCC 3′. Which of the following sequences would not be recognized by this enzyme? A. 3′ TCTTAAG 5′ B. 5′ AGCGGATCC 3′ C. 5′ AGGATCCGTA 3′ D. 3′ CCTAGGATC 5′
answer
A This sequence does not contain the BamHI recognition site.
question
Which of the following statements about ddNTPs is true? A. They have a free 3′‑hydroxyl group on the sugar. B. They have a hydrogen at the 3′ carbon of the sugar. C. They have an oxygen at the 2′ carbon of the sugar. D. DNA polymerase can add a new dNTP to a 3′ ddNTP.
answer
B ddNTPs terminate synthesis because there is no 3′‑hydroxyl group onto which DNA polymerase can add nucleotides.
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DNA fragments that are 600 bp long will migrate more quickly through a sequencing gel than fragments that are 150 bp long. A. True B. False
answer
B Small DNA fragments have less hindrance in moving through the gel, so they migrate more quickly than larger fragments.
question
Which of the following statements about manual Sanger sequencing is true? A. The DNA sequence obtained is complementary to the template strand. B. Each of the four terminating ddNTPs is labeled with a different fluorescent dye. C. The DNA sequence is read from the top of the gel to the bottom. D. One sequencing reaction is performed.
answer
A The DNA fragments produced in sequencing reactions are synthesized by DNA polymerase to be complementary to the template strand.
question
In which section of the search results can you find nucleotide-by-nucleotide comparisons between your query sequence and similar database sequences? A. Graphic Summary B. Descriptions C. Alignments
answer
C. Alignments
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Now that you understand what E values mean, you can determine which hit or hits represent the best match(es) to your query sequence. A. Only one hit derived from Fusarium oxysporum is the best match to the query sequence. B. Several hits derived from Fusarium oxysporum are best matches to the query sequence. C. Only one hit derived from Fusarium redolens is the best match to the query sequence. D. Several hits derived from Fusarium redolens are best matches to the query sequence.
answer
B. Several hits derived from Fusarium oxysporum are best matches to the query sequence.
question
Only mutations that involve chromosomal rearrangements can result in the fusion of two different genes, which could code for a chimeric protein such as the BCR-ABL protein. Simple point mutations--insertion, deletion, or replacement of a single nucleotide--do not result in the fusion of two different genes. A. duplication B. translocation C. inversion D. deletion
answer
B. Translocation
question
A Robertsonian translocation is considered non-reciprocal because _______. A. trisomies of chromosome 21 are viable, whereas monosomies of the same chromosome are not B. the smaller of the two reciprocal products of translocated chromosomes is lost C. for every viable gamete formed, there are two inviable gametes formed D. an uneven number of gametes is produced in each meiosis
answer
B. the smaller of the two reciprocal products of translocated chromosomes is lost
question
Which of the following statements regarding familial Down syndrome is false? A. If one parent is a translocation heterozygote for chromosomes 14/21, a child born to this parent is as likely to have Down syndrome as he is to be normal. B. Heterozygous carriers of the Robertsonian translocation that cause familial Down syndrome can have children who are also carriers of the translocation. C. It accounts for approximately 5% of all Down syndrome cases. D. Heterozygous carriers of the Robertsonian translocation that causes familial Down syndrome can have children who are phenotypically normal and are not carriers of the translocation.
answer
A. If one parent is a translocation heterozygote for chromosomes 14/21, a child born to this parent is as likely to have Down syndrome as he is to be normal.
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With respect to the chromosomes involved in the translocation, 14 and 21, what is the total number of different gametes possible for a heterozygous carrier parent to produce? A. 6 B. 2 C. 3 D. 4
answer
D. 6
question
Cancer is best described as a ________. A. genetic disorder at the cellular level B. bacterial disease at the somatic cell level C. genetic disease at the gametic cell level D. viral disease
answer
A. genetic disorder at the cellular level
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All of the following are characteristics of genomic instability in cancer cells EXCEPT __________. A. DNA amplification B. chromosomal deletions C. chromosomal translocations D. controlled cell division
answer
D. controlled cell division
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What is the relationship between proto-oncogenes and oncogenes? A. Oncogenes are mutant forms of proto-oncogenes. B. Both are involved in arresting the cell cycle. C. Both must be activated to halt cell division. D. Oncogenes are versions of proto-oncogenes that have been permanently switched off.
answer
A. Oncogenes are mutant forms of proto-oncogenes.
question
Which of the following statements describes metastasis? A. It is the ability to divide uncontrollably. B. A class of genes that initiate apoptosis C. Loss of contact inhibition D. The ability to form secondary tumors at another site
answer
D. The ability to form secondary tumors at another site
question
Distinguish between oncogenes and proto-oncogenes. A. Proto-oncogenes are genes that induce or maintain uncontrolled cellular proliferation associated with cancer. They are mutant forms of oncogenes, which normally function to regulate cell division. B. Oncogenes are genes that induce or maintain uncontrolled cellular proliferation associated with cancer. They are mutant forms of proto-oncogenes, which normally function to regulate cell division.
answer
B. Oncogenes are genes that induce or maintain uncontrolled cellular proliferation associated with cancer. They are mutant forms of proto-oncogenes, which normally function to regulate cell division.
question
In what ways can proto-oncogenes be converted to oncogenes? Check all that apply. A. point mutations B. repositioning of regulatory sequences C. gene amplification D. translocations
answer
A. point mutations B. repositioning of regulatory sequences C. gene amplification D. translocations
question
Of the two classes of genes associated with cancer, tumor-suppressor genes and oncogenes, mutations in which group can be considered gain-of-function mutations? A. tumor-suppressor genes B. oncogenes
answer
B. Ocogenes
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In which group are the loss-of-function mutations? A. tumor-suppressor genes B. oncogenes
answer
A. tumor-suppressor genes
question
Sometimes, a mother who is affected with a mitochondrial disease will have an unaffected child. Which of the following could explain this observation? Select all that apply. A. The phenotype could be affected by nuclear genes, which could differ among children. B. One or more of the children could inherit the majority of their mitochondria from an unaffected father. C. The affected mother could be heteroplasmic. D. Environmental factors (such as taking antibiotics) could affect expression of the phenotype.
answer
A. The phenotype could be affected by nuclear genes, which could differ among children. C. The affected mother could be heteroplasmic. D. Environmental factors (such as taking antibiotics) could affect expression of the phenotype.
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Given that these are debilitating conditions, why has no cure been developed? A. The defective mitochondria would need to be identified for a cure to be achieved, and that appears to be technologically impossible at this time. B. The defective mitochondria would need to be corrected for a cure to be achieved, and that appears to be technologically impossible at this time. C. The defective mitochondria would need to be corrected for a cure to be achieved, and that may cause damage to the whole organism. D. The defective mitochondria would need to be corrected for a cure to be achieved, and that appears to be very expensive.
answer
B. The defective mitochondria would need to be corrected for a cure to be achieved, and that appears to be technologically impossible at this time.
question
Can you suggest a general approach that might be used to treat, or perhaps even cure, these disorders? A. Favor the replication of both mutant and normal mitochondria. B. Suppress the replication of normal mitochondria and favor the replication of mutant mitochondria. C. Suppress the replication of mutant mitochondria and favor the replication of normal mitochondria. D. Suppress the replication of both mutant and normal mitochondria.
answer
C. Suppress the replication of mutant mitochondria and favor the replication of normal mitochondria.
question
Compared with the vast number of mitochondria in an embryo, the number of mitochondria in an ovum is relatively small. Might such an ooplasmic mitochondrial bottleneck present an opportunity for therapy or cure? A. It may be possible to cure it by increasing mitochondria number in any way. B. It may be possible to alter the heteroplasmic ratio by favoring replication of mitochondria. C. It may be possible to alter the heteroplasmic ratio by microinjection of mitochondria. D. No, there is no opportunity.
answer
C. It may be possible to alter the heteroplasmic ratio by microinjection of mitochondria.