Question 1

Which structural event marks the transition from prophase to prometaphase during mitosis?

Accepted Answer

Breakdown of the nuclear envelope

Question 2

During anaphase I of meiosis, what is separated and moved to opposite poles of the cell?

Accepted Answer

Homologous chromosomes

Question 3

A cell fails to properly align its chromosomes before mitosis, but proceeds anyway. Which checkpoint failed, and what is a likely consequence?

Accepted Answer

Spindle Assembly Checkpoint (SAC); aneuploidy

Question 4

Which equation best represents the hydrolysis of GTP during translation elongation?

Accepted Answer

$$\mathrm{GTP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{GDP} + \mathrm{P}_i$$

Question 5

In animal cells, cytokinesis is accomplished by which mechanism?

Accepted Answer

Pinching in of the cell membrane by a contractile ring

Question 6

Which subunit of bacterial RNA polymerase is essential for promoter recognition?

Accepted Answer

Sigma ($$\sigma) $$factor

Question 7

A mutation changes a codon from $$\mathrm{UAC} ($$tyrosine) to $$\mathrm{UAA} ($$stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 8

Which of the following is NOT a required step for pre-mRNA processing before export from the nucleus?

Accepted Answer

Removal of exons

Question 9

What is the function of Exon Junction Complexes (EJCs) in nonsense-mediated decay (NMD)?

Accepted Answer

They signal the presence of a premature stop codon, triggering mRNA degradation

Question 10

Cellobiase acts on p-nitrophenyl glucopyranoside. After adding a basic stop solution, which colored product is formed?

Accepted Answer

p-nitrophenol (yellow)

Question 11

During translation, which ribosomal site is occupied by the tRNA carrying the growing polypeptide chain?

Accepted Answer

P site (peptidyl site)

Question 12

A patient’s cells exhibit frequent aneuploidy. Which cell cycle checkpoint is most likely defective?

Accepted Answer

Spindle Assembly Checkpoint (SAC)

Question 13

Which of the following best describes the difference between cytokinesis in plant and animal cells?

Accepted Answer

Animal cells use a cleavage furrow; plant cells form a cell plate from vesicles

Question 14

Which stage of translation requires GTP hydrolysis for ribosome assembly?

Accepted Answer

Initiation

Question 15

A missense mutation in a gene results in which of the following?

Accepted Answer

A change in a single amino acid in the protein

Question 16

Which event occurs during mitotic anaphase?

Accepted Answer

Sister chromatids separate and move to opposite poles

Question 17

A scientist observes that after splicing, certain proteins remain bound at exon-exon junctions. What is the role of these proteins?

Accepted Answer

They are Exon Junction Complexes (EJCs) that help identify abnormal mRNAs for NMD

Question 18

Which of the following is a direct consequence of a nonsense mutation?

Accepted Answer

A truncated protein due to a premature stop codon

Question 19

Which of the following steps in pre-mRNA processing is essential for ribosome binding during translation?

Accepted Answer

Addition of a 5' cap

Question 20

A researcher is studying the effect of cellobiase on p-nitrophenyl glucopyranoside. Which equation represents the reaction that produces the colored product?

Accepted Answer

$$	ext{p-nitrophenyl glucopyranoside} + 	ext{H}_2	ext{O} \xrightarrow{	ext{cellobiase}} 	ext{glucose} + 	ext{p-nitrophenol}$$

Key Concepts in Cell Division, Gene Expression, and Molecular Biology

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