Question 1

A researcher is studying a cell line that divides uncontrollably and is resistant to chemotherapy drugs that target microtubules. Which phase of the cell cycle is most directly affected by these drugs, and why does this make them effective against cancer cells?

Accepted Answer

M phase, because microtubules form the mitotic spindle required for chromosome separation during mitosis.

Question 2

During DNA replication, the lagging strand is synthesized in short fragments. Which enzyme is responsible for joining these fragments, and what is the name of these fragments?

Accepted Answer

DNA ligase; Okazaki fragments

Question 3

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this, and what is the likely effect on the protein?

Accepted Answer

Nonsense mutation; the protein will be prematurely truncated.

Question 4

Which of the following best explains why siblings from the same parents are genetically unique (except for identical twins)?

Accepted Answer

Crossing over during Prophase I of meiosis and independent assortment of chromosomes.

Question 5

A scientist uses PCR to amplify a DNA segment. Which enzyme is essential for this process, and why is it chosen over other DNA polymerases?

Accepted Answer

Taq polymerase, because it is heat-stable and can withstand the high temperatures used to denature DNA.

Question 6

Which of the following best describes the role of cyclins and Cdks in the cell cycle?

Accepted Answer

Cyclins and Cdks form complexes that regulate progression through cell cycle checkpoints.

Question 7

A patient is found to have a mutation that prevents the formation of the 5' cap on mRNA. Which of the following is a likely consequence?

Accepted Answer

The mRNA will be rapidly degraded and may not be efficiently translated.

Question 8

Which repair mechanism is most likely to introduce errors (insertions or deletions) when fixing double-strand breaks in DNA?

Accepted Answer

Non-homologous end joining (NHEJ)

Question 9

A retrovirus infects a human cell. Which enzyme does it use to integrate its genetic material into the host genome, and what is the direction of information flow?

Accepted Answer

Reverse transcriptase; RNA → DNA

Question 10

A scientist wants to cut a gene from one organism and insert it into a plasmid vector. Which two tools are essential for this process?

Accepted Answer

Restriction enzymes and DNA ligase

Question 11

Which of the following best explains why chemotherapy drugs that disrupt microtubule function can cause side effects such as hair loss and digestive issues?

Accepted Answer

These drugs target all rapidly dividing cells, not just cancer cells.

Question 12

Which of the following is a direct result of a frameshift mutation in a gene?

Accepted Answer

All codons downstream of the mutation are altered, often resulting in a nonfunctional protein.

Question 13

A cell is observed to have 46 chromosomes at the start of mitosis. After cytokinesis, how many chromosomes will each daughter cell have?

Accepted Answer

$$46$$

Question 14

Which of the following best describes the function of the poly-A tail added to eukaryotic mRNA?

Accepted Answer

It protects the mRNA from degradation and aids in export from the nucleus.

Question 15

A scientist is using gel electrophoresis to analyze DNA fragments. Which statement best explains why smaller DNA fragments move farther through the gel?

Accepted Answer

Smaller fragments experience less resistance and can travel more easily through the gel matrix.

Question 16

Which of the following is a key ethical concern for Institutional Review Boards (IRBs) overseeing clinical research?

Accepted Answer

Preventing undue influence by ensuring compensation does not coerce participation.

Question 17

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Homologous chromosomes are a matched pair from each parent; sister chromatids are identical copies of a single chromosome.

Question 18

A new drug is developed that blocks the function of aminoacyl-tRNA synthetase. What is the most immediate effect on protein synthesis?

Accepted Answer

tRNAs cannot be loaded with amino acids, so translation cannot proceed.

Question 19

Which of the following best explains why the number of chromosomes does not correlate with organismal complexity?

Accepted Answer

Chromosome number varies widely among species and is not related to the amount of genetic information or complexity.

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