Question 1

Which of the following best describes the role of the p53 protein in cancer genetics?

Accepted Answer

It is a tumor-suppressor protein that regulates cell division, apoptosis, and DNA repair, earning the nickname 'guardian of the genome'.

Question 2

Alfred Knudson's multistep model of cancer, based on retinoblastoma, proposes that:

Accepted Answer

Two separate genetic defects are required for cancer to develop, often involving both alleles of a tumor-suppressor gene.

Question 3

Which equation best represents the probability ($$P) $$that a person heterozygous for a tumor-suppressor gene will develop cancer if the loss of heterozygosity occurs with probability $$p_{loh}$$ and the initial mutation occurs with probability $$p_{mut}$$?

Accepted Answer

$$P = p_{loh} 	imes p_{mut}$$

Question 4

Which of the following is a key difference between oncogenes and tumor-suppressor genes?

Accepted Answer

Oncogenes are dominant-acting and stimulate cell proliferation when mutated, while tumor-suppressor genes are recessive-acting and lose their inhibitory function when both alleles are mutated.

Question 5

A patient is diagnosed with chronic myelogenous leukemia. Which chromosomal abnormality is most likely present?

Accepted Answer

A reciprocal translocation between chromosomes 9 and 22.

Question 6

Which environmental factor is attributed to the highest percentage of cancer cases in the United Kingdom, according to Table 23.3?

Accepted Answer

Tobacco

Question 7

The Ras signal-transduction pathway is important in cancer because:

Accepted Answer

Mutations in Ras can lead to continuous stimulation of cell division, contributing to cancer development.

Question 8

Which of the following best explains why cancer is considered a genetic disease, but most cancers are not inherited?

Accepted Answer

Most cancers arise from somatic mutations and environmental factors, not from inherited germline mutations.

Question 9

Which process describes the spread of cancer cells from a primary tumor to form secondary tumors in other tissues?

Accepted Answer

Metastasis

Question 10

A mutation in the RB protein affects which cell cycle checkpoint, and what is the consequence?

Accepted Answer

G1/S checkpoint; cells may undergo uncontrolled DNA replication

Question 11

Epigenetic changes in cancer often involve alterations in DNA methylation. Which statement is correct?

Accepted Answer

Hypomethylation and hypermethylation can both contribute to cancer, and these changes are reversible.

Question 12

Colorectal cancer progression is best explained by:

Accepted Answer

Sequential mutations in multiple genes, leading to increasingly aggressive tumor cells.

Question 13

Which of the following equations best models the clonal evolution of tumor cells, where $$N is $$the number of mutations and $$A is $$the aggressiveness of the tumor?

Accepted Answer

$$A = e^N$$

Question 14

A reciprocal translocation between chromosomes 8 and 14 is associated with which type of cancer?

Accepted Answer

Burkitt lymphoma

Question 15

Which of the following is NOT a typical chromosomal abnormality found in cancer cells?

Accepted Answer

Perfectly normal karyotype

Question 16

Retroviruses can contribute to cancer development by:

Accepted Answer

Mutating and rearranging proto-oncogenes or inserting strong promoters near proto-oncogenes.

Question 17

Which human virus is most strongly associated with cervical cancer?

Accepted Answer

Human papillomavirus (HPV)

Question 18

Loss of heterozygosity in a tumor-suppressor gene can predispose an individual to cancer. Which genotype is most at risk after a chromosome deletion?

Accepted Answer

Heterozygous (Aa)

Question 19

Which of the following best describes the function of cyclin-dependent kinases (CDKs) in the cell cycle?

Accepted Answer

They phosphorylate target proteins to regulate progression through cell cycle checkpoints.

Question 20

A mutation in the APC gene is most likely to contribute to which type of cancer?

Accepted Answer

Colorectal cancer

Cancer Genetics: Mechanisms, Genes, and Environmental Factors

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