Question 1

Which of the following is true of the BRCA1 gene?&#10;A)Its product normally functions in DNA repair.&#10;B)Germ-line mutations in this gene are associated with an increased risk for breast and ovarian cancers.&#10;C)Somatic mutations in this gene are associated with an increased risk for ovarian cancer.&#10;D)A,B,and C.&#10;E)None of the above.

Accepted Answer

The BRCA1 gene's product normally functions in DNA repair. Germ-line mutations in this gene are associated with an increased risk for breast and ovarian cancers. Somatic mutations in this gene are associated with an increased risk for ovarian cancer.

Question 2

Which of the following may result in loss of function of a tumor suppressor gene?&#10;A)Nondisjunction of sister chromatids&#10;B)Failure of a chromatid containing a tumor suppressor gene to attach to a spindle fiber during cell division&#10;C)Hypermethylation of the promoter for the gene&#10;D)A,B,and C&#10;E)None of the above

Accepted Answer

All the options listed can lead to the loss of function of a tumor suppressor gene. Nondisjunction and failure of attachment to spindle fibers can result in loss of a chromosome containing the gene, while hypermethylation of the promoter can silence gene expression.

Question 3

Keratoses,or benign skin lesions,often exhibit&#10;A)Mutant p53 alleles.&#10;B)Mutations carrying a dipyrimidine substitution.&#10;C)Mutations resulting from exposure to UV light.&#10;D)A,B,and C.&#10;E)None of the above.

Accepted Answer

Keratoses, or benign skin lesions, often exhibit characteristics such as mutant p53 alleles, mutations carrying a dipyrimidine substitution, and mutations resulting from exposure to UV light. These features are indicative of the DNA damage and cellular changes that can occur due to UV exposure, which is a common cause of such skin lesions.

Question 4

Mutations that result in compromised function of the spindle assembly checkpoint during mitosis may directly contribute to&#10;A)Impaired p53 function.&#10;B)Impaired DNA replication.&#10;C)Aneuploidy.&#10;D)A and B.&#10;E)None of the above.

Accepted Answer

The spindle assembly checkpoint ensures that chromosomes are properly aligned and attached to the spindle fibers before cell division proceeds. If this checkpoint is compromised due to mutations, chromosomes may not be properly separated and distributed to daughter cells, leading to aneuploidy (an abnormal number of chromosomes) which is associated with cancer development. Impaired p53 function and impaired DNA replication are not directly related to the spindle assembly checkpoint.

Question 5

The DNA polymerase pol-&#948;&#10;A)Is involved in DNA synthesis.&#10;B)Is involved in proofreading newly synthesized DNA.&#10;C)Exhibits exonuclease activity.&#10;D)A,B,and C.&#10;E)None of the above.

Accepted Answer

DNA polymerase pol-δ is involved in DNA synthesis and has proofreading ability through its exonuclease activity, making options A, B, and C all correct.

Question 6

Which of the following mechanisms is involved in double-strand DNA repair?&#10;A)Homology-dependent repair&#10;B)Nonhomologous end joining&#10;C)Mismatch repair&#10;D)A and B&#10;E)A,B,and C

Accepted Answer

Double-strand DNA repair can occur through either homology-dependent repair (HDR) or nonhomologous end joining (NHEJ). HDR requires a template for repair and uses homologous DNA sequences to repair the damaged DNA strand. NHEJ, on the other hand, simply rejoins the broken ends of the DNA without reliance on homology. Therefore, both A and B are mechanisms involved in double-strand DNA repair. Mismatch repair (C) is not related to double-strand DNA repair and is involved in correcting mistakes made during DNA replication.

Question 7

A patient with chronic myelogenous leukemia CML)exhibits chromosomal translocations in both lymphocytes and myeloid cells.This suggests that the cell in which the initiating mutation occurred was MOST likely

A)A lymphocyte.
B)A macrophage.
C)A neutrophil.
D)A hematopoietic stem cell.
E)A myeloid precursor.

Accepted Answer

Both lymphocytes and myeloid cells are derived from hematopoietic stem cells. Therefore, the initiating mutation must have occurred in a cell that gave rise to both lymphocytes and myeloid cells, which is a hematopoietic stem cell.

Question 8

Which of the following may result in point mutations that can contribute to cancer?&#10;A)Deamination of 5-methylcytosine&#10;B)Unrepaired single-strand breaks during DNA synthesis&#10;C)Microsatellite instability&#10;D)Exposure to UV radiation&#10;E)All of the above

Accepted Answer

All of the above options may result in point mutations that can contribute to cancer. 
- Deamination of 5-methylcytosine can result in a C to T transition mutation, which may lead to changes in the protein-coding sequence and contribute to cancer development.
- Unrepaired single-strand breaks during DNA synthesis can lead to errors in replication and mutations, which may contribute to cancer when the mutations affect genes involved in cell cycle regulation or DNA repair.
- Microsatellite instability is a type of DNA replication error that can result in changes in the number of repeats of short DNA sequences, which can affect gene expression and contribute to cancer development.
- Exposure to UV radiation can cause DNA damage, including the formation of pyrimidine dimers, which may result in mutations that contribute to skin cancer development.

Question 9

Which of the following types of cells are most protected from genomic damage?&#10;A)Stem cells&#10;B)Differentiated cells&#10;C)Transit-amplifying cells&#10;D)Dividing cells&#10;E)A,B,and C

Accepted Answer

Stem cells have mechanisms in place to protect their genome from damage, including specialized DNA repair pathways, as they need to maintain their ability to self-renew and differentiate into different cell types. Differentiated, transit-amplifying, and dividing cells may have some level of protection but not to the same extent as stem cells.

Question 10

The chemical structure formed from the reaction of a DNA base with a carcinogen is called&#10;A)A lesion.&#10;B)An adduct.&#10;C)An ultimate carcinogen.&#10;D)A xenobiotic.&#10;E)None of the above.

Accepted Answer

The chemical structure formed from the reaction of a DNA base with a carcinogen is called an adduct. A lesion refers to any abnormality or damage in DNA, not specifically from a carcinogen. An ultimate carcinogen is a type of carcinogen that has been metabolized in the body to become active and able to damage DNA. Xenobiotic refers to any foreign substance in the body, not specifically carcinogens. Therefore, the best choice is B, an adduct.

Question 11

Defects in which of the following cellular processes may contribute to an increased incidence of cancer?&#10;A)Nucleotide-excision repair&#10;B)Mismatch repair&#10;C)Base-excision repair&#10;D)A ,B,and C&#10;E)None of the above

Accepted Answer

The answer of Defects in which of the following cellular...

Question 12

Which of the following types of mutations are advantageous to cancer cell growth?&#10;A)Those resulting in defective mismatch repair&#10;B)Inherited defects in double-strand DNA repair&#10;C)A defect in nucleotide-excision repair&#10;D)A,B,and C&#10;E)None of the above

Accepted Answer

The answer of Which of the following types of mutations...

Deck 12: Maintenance of Genomic Integrity and the Development of Cancer