Question 1

Which of the following best describes the primary function of the nucleolus within the nucleus?

Accepted Answer

It is responsible for the assembly of ribosomal subunits.

Question 2

A mutation disrupts the structure of the nuclear lamina. Which of the following cellular processes is most likely to be directly affected?

Accepted Answer

Structural support and shape of the nucleus

Question 3

The nuclear envelope consists of which of the following components?

Accepted Answer

An outer membrane, an inner membrane, and the perinuclear space

Question 4

Which of the following statements about nuclear pore complexes (NPCs) is correct?

Accepted Answer

NPCs are built from nucleoporins and have octagonal symmetry.

Question 5

A protein destined for the nucleus contains a nuclear localization signal (NLS). Which of the following best describes the role of importin in this process?

Accepted Answer

Importin binds to the NLS-containing cargo and facilitates its transport through the nuclear pore complex.

Question 6

Which of the following best explains why mature mRNA must be exported from the nucleus?

Accepted Answer

mRNA is translated into protein in the cytoplasm.

Question 7

During nuclear import, what is the role of Ran-GTP?

Accepted Answer

Ran-GTP binds to importin, causing release of the cargo protein inside the nucleus.

Question 8

A scientist is studying a disease in which exportin is nonfunctional. Which of the following processes would be most directly impaired?

Accepted Answer

Export of mature tRNA to the cytoplasm

Question 9

Which of the following best describes the perinuclear space?

Accepted Answer

It is the region between the inner and outer nuclear membranes.

Question 10

A mutation in the gene encoding a nucleoporin would most likely affect which of the following?

Accepted Answer

The structure and function of the nuclear pore complex

Question 11

Which of the following is a correct sequence of events for nuclear import of a protein with a nuclear localization signal (NLS)?

Accepted Answer

Cargo binds importin → Transport through NPC → Importin binds Ran-GTP → Cargo released in nucleus

Question 12

Which of the following best explains why the nuclear envelope is considered a double membrane structure?

Accepted Answer

It consists of two lipid bilayers: an inner and an outer membrane, separated by the perinuclear space.

Question 13

A patient has a genetic defect that prevents the hydrolysis of GTP by Ran. Which step in nuclear export would be directly affected?

Accepted Answer

Release of cargo in the cytosol

Question 14

Which of the following is NOT a function of the nucleus?

Accepted Answer

Translation of mRNA into protein

Question 15

Which of the following best describes the function of the nuclear lamina?

Accepted Answer

It provides structural support to the nucleus and is made of lamins.

Question 16

A researcher adds a mutation to a protein that removes its nuclear localization signal (NLS). What is the most likely outcome?

Accepted Answer

The protein will remain in the cytoplasm and not enter the nucleus.

Question 17

Which of the following best explains the directionality of nuclear import and export?

Accepted Answer

The gradient of Ran-GTP and Ran-GDP across the nuclear envelope determines directionality.

Question 18

Which of the following molecules would require active transport through the nuclear pore complex?

Accepted Answer

A 60S ribosomal subunit

Question 19

Which of the following best describes the role of the perinuclear space in the nuclear envelope?

Accepted Answer

It separates the inner and outer nuclear membranes and is continuous with the lumen of the endoplasmic reticulum.

Question 20

A cell is observed to have defective transport of gene regulatory proteins into the nucleus. Which of the following is the most likely cause?

Accepted Answer

A mutation in the importin protein complex

The Nucleus: Structure, Function, and Transport Mechanisms

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