Question 1

Which of the following best explains why DNA can code for all the proteins in a cell, despite having only four types of nucleotide bases?

Accepted Answer

The sequence of three nucleotide bases (codon) codes for one of 20 amino acids, allowing for many combinations.

Question 2

In female mammals, X-inactivation is a mechanism for gene dosage compensation. Which of the following statements is TRUE regarding this process?

Accepted Answer

One X chromosome is randomly inactivated in each cell, resulting in mosaic gene expression.

Question 3

A point mutation in DNA results in a base substitution. Which of the following outcomes is most likely if the mutation changes a codon but does NOT alter the amino acid sequence of the protein?

Accepted Answer

A silent mutation will occur due to the degeneracy of the genetic code.

Question 4

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

Accepted Answer

Proto-oncogenes stimulate cell proliferation, while tumor suppressor genes inhibit cell proliferation.

Question 5

A woman is heterozygous for a gene located on the X chromosome. Due to X-inactivation, which of the following is most likely to be observed in her somatic cells?

Accepted Answer

Some cells express the maternal allele, while others express the paternal allele.

Question 6

Which checkpoint in the cell cycle ensures that the cell is large enough to divide, has enough nutrients, and that the DNA is undamaged before proceeding?

Accepted Answer

G1 checkpoint

Question 7

A mutation in the p53 gene can lead to which of the following consequences?

Accepted Answer

Loss of cell cycle arrest and increased genomic instability

Question 8

A patient with Li-Fraumeni syndrome has inherited a germline mutation in one allele of the p53 gene. What is the most likely explanation for their increased cancer risk?

Accepted Answer

A second somatic mutation in the remaining normal allele can lead to loss of p53 function in some cells.

Question 9

Which of the following best describes apoptosis?

Accepted Answer

Programmed cell death involving orderly breakdown of cellular components

Question 10

A frameshift mutation is most likely to result from which of the following DNA changes?

Accepted Answer

An addition or deletion of nucleotides not in multiples of three

Question 11

Which of the following is a key function of the G2/M checkpoint in the cell cycle?

Accepted Answer

Verifying that DNA replication is complete and undamaged before mitosis

Question 12

A cell is found to have a mutation that causes a proto-oncogene to become an oncogene. Which of the following is the most likely result?

Accepted Answer

The cell will divide uncontrollably, increasing the risk of cancer.

Question 13

Which of the following best explains why cancer is considered a clonal disease?

Accepted Answer

Cancer cells originate from a single cell that acquires mutations and proliferates.

Question 14

A researcher observes that a cell with excessive DNA damage undergoes apoptosis. Which protein is most likely responsible for sensing the damage and triggering this response?

Accepted Answer

p53

Question 15

Which of the following scenarios best illustrates the concept of gene dosage compensation in mammals?

Accepted Answer

A female with two X chromosomes inactivates one X in each cell, balancing gene expression with males.

Question 16

Which of the following is a likely consequence if the spindle assembly checkpoint fails during mitosis?

Accepted Answer

Chromosomes may not be properly segregated, leading to aneuploidy.

Question 17

A patient inherits a mutation in the BRCA1 gene. Which of the following best describes the role of BRCA1 in preventing cancer?

Accepted Answer

BRCA1 is a tumor suppressor gene involved in DNA repair.

Question 18

Which of the following best describes the process of clonal evolution in cancer development?

Accepted Answer

Cancer cells accumulate additional mutations over time, leading to more aggressive clones.

Question 19

A cell with a nonfunctional tumor suppressor gene is most likely to:

Accepted Answer

Divide uncontrollably due to loss of growth inhibition.

Question 20

Which of the following equations best represents the relationship between the number of possible codons ($$N) $$and the number of nucleotide bases ($$b) in a $$codon of length $$n$$?

Accepted Answer

$$N = b^n$$

Genetic Information Transfer, Mutation, and Cancer: Key Concepts in General Biology

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