MCAT Biology 2

Question 1

Which enzyme is responsible for removing RNA primers during DNA replication in eukaryotes?

Accepted Answer

RNase H combined with FEN1

Answer

In eukaryotes, RNase H and FEN1 (flap endonuclease 1) work together to remove RNA primers, after which DNA polymerase δ fills the gap.

Question 2

A cell in G2 phase is treated with a drug that prevents microtubule polymerization. At which checkpoint will cell cycle arrest most likely occur?

Accepted Answer

G2/M checkpoint

Answer

The G2/M checkpoint monitors whether DNA replication is complete and cellular machinery (including microtubules for the spindle) is ready before mitosis begins.

Question 3

Which type of RNA processing is unique to eukaryotes and involves joining of non-contiguous sequences?

Accepted Answer

RNA splicing

Answer

RNA splicing removes introns and joins exons, creating a mature mRNA from non-contiguous coding sequences—a process absent in prokaryotes.

Question 4

During which stage of cellular respiration is the most ATP produced per molecule of glucose?

Accepted Answer

Oxidative phosphorylation

Answer

Oxidative phosphorylation generates approximately 32-34 ATP via chemiosmosis driven by the electron transport chain, far exceeding all other stages.

Question 5

A mutation in which of the following would most directly impair the ability of a eukaryotic cell to target proteins to the endoplasmic reticulum?

Accepted Answer

Signal recognition particle (SRP)

Answer

The signal recognition particle recognizes the signal sequence on nascent polypeptides and directs ribosomes to the ER membrane for cotranslational translocation.

MCAT - Medical College Admission Test Practice Test

MCAT - Medical College Admission Test Practice Test

MCAT Biology 2