Question 1

Which of the following best explains why loss-of-function mutations in the p53 gene can lead to increased cancer risk?

Accepted Answer

p53 is a tumor suppressor gene that normally induces cell-cycle arrest or apoptosis in response to DNA damage, so its loss allows damaged cells to survive and proliferate.

Question 2

A patient is diagnosed with chronic myelogenous leukemia (CML). Cytogenetic analysis reveals a translocation between chromosomes 9 and 22, resulting in the Philadelphia chromosome. What is the molecular consequence of this translocation?

Accepted Answer

It creates a fusion gene (BCR-ABL) that encodes a constitutively active tyrosine kinase.

Question 3

Which of the following scenarios would most likely result in tumor formation according to the balance of cell division and apoptosis?

Accepted Answer

Normal cell division and decreased apoptosis

Question 4

Which protein is often lost in cancer cells, resulting in decreased cell-cell adhesion and increased invasiveness?

Accepted Answer

E-cadherin

Question 5

A single gain-of-function mutation in a proto-oncogene can convert it into an oncogene. Which of the following best describes the inheritance pattern of such mutations?

Accepted Answer

Dominant; only one allele needs to be mutated

Question 6

Which of the following is NOT a typical mechanism by which a proto-oncogene can be converted into an oncogene?

Accepted Answer

Loss-of-function mutation

Question 7

A child inherits a loss-of-function mutation in one copy of the Rb gene. Which of the following events must occur for retinoblastoma to develop?

Accepted Answer

A second loss-of-function mutation in the remaining normal Rb allele

Question 8

Which of the following best describes the role of tumor suppressor genes in cancer?

Accepted Answer

Their loss or inactivation removes restraints on cell division, contributing to cancer.

Question 9

Which of the following is a real-world example of a targeted cancer therapy, and what is its mechanism?

Accepted Answer

Imatinib (Gleevec); inhibits the Bcr-Abl tyrosine kinase produced by the Philadelphia chromosome

Question 10

Which of the following environmental factors is most strongly associated with increased risk of lung cancer?

Accepted Answer

Cigarette smoking

Question 11

A mutation in the Ras gene results in a protein that is always bound to GTP. What is the likely consequence for the cell?

Accepted Answer

The cell will receive constant proliferative signals, increasing the risk of cancer.

Question 12

Which of the following best explains why cancer cells are often genetically unstable?

Accepted Answer

They accumulate mutations in genes responsible for DNA repair, leading to higher mutation rates.

Question 13

Which of the following is a hallmark of metastatic cancer cells?

Accepted Answer

They can invade surrounding tissues and colonize distant organs.

Question 14

Which of the following best describes the difference between oncogenes and tumor suppressor genes?

Accepted Answer

Oncogenes promote cell survival and proliferation when activated, while tumor suppressor genes restrain cell division and promote apoptosis when functional.

Question 15

Which of the following is a common feature of cancer cells grown in culture, as opposed to normal cells?

Accepted Answer

They form foci of uninhibited transformed cells due to loss of contact inhibition.

Question 16

Which of the following best describes the multi-step nature of tumorigenesis in colorectal carcinoma?

Accepted Answer

Multiple genetic changes, including mutations in APC, Ras, and p53, are typically required for progression from normal epithelium to carcinoma.

Question 17

Which of the following is a direct effect of radiation therapy in cancer treatment?

Accepted Answer

It causes chromosomal damage, preventing mitosis in cancer cells.

Question 18

Which of the following best explains why both alleles of a tumor suppressor gene typically must be inactivated to contribute to cancer?

Accepted Answer

One functional allele is usually sufficient to restrain cell proliferation.

Question 19

Which of the following is a real-world example of a carcinogen and its associated cancer type?

Accepted Answer

Aflatoxin; liver cancer

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