Question 1

Which of the following best describes the structure of the nuclear envelope in eukaryotic cells?

Accepted Answer

It consists of a double membrane separated by a perinuclear space, with the outer membrane continuous with the endoplasmic reticulum.

Question 2

What is the primary function of the nuclear pore complex (NPC)?

Accepted Answer

To mediate the passage of molecules between the cytosol and nucleoplasm.

Question 3

A protein destined for the nucleus contains a nuclear localization signal (NLS). Which amino acids are most commonly found in NLS sequences?

Accepted Answer

Lysine and arginine

Question 4

During nuclear import via the Ran/Importin pathway, what triggers the release of the NLS-containing protein from importin inside the nucleus?

Accepted Answer

Association of importin with Ran-GTP

Question 5

Which protein maintains high levels of Ran-GTP inside the nucleus?

Accepted Answer

Guanine-nucleotide exchange factor (GEF)

Question 6

What is the role of nuclear export signals (NES) in RNA export from the nucleus?

Accepted Answer

They are recognized by exportins, which mediate transport of RNA-protein complexes out of the nucleus.

Question 7

The nuclear lamina is primarily composed of which type of cytoskeletal filament?

Accepted Answer

Intermediate filaments called lamins

Question 8

Which of the following best explains the symptoms of Hutchinson-Gilford Progeria Syndrome (HGPS) at the cellular level?

Accepted Answer

Defective processing of lamin A leads to a weakened nuclear lamina, resulting in abnormal nuclear structure and impaired cellular function.

Question 9

Which phase of the cell cycle is characterized by the doubling of nuclear DNA?

Accepted Answer

S phase

Question 10

DNA replication is described as semiconservative. What does this mean?

Accepted Answer

Each new DNA molecule consists of one parental strand and one newly synthesized strand.

Question 11

In E. coli, which enzyme is responsible for unwinding the DNA strands during replication?

Accepted Answer

DnaB (DNA helicase)

Question 12

What is the function of single-stranded binding protein (SSB) during DNA replication?

Accepted Answer

It stabilizes unwound DNA strands to prevent them from re-annealing.

Question 13

Which of the following statements about eukaryotic DNA replication origins is correct?

Accepted Answer

Replication is initiated at multiple origins, creating several replicons per chromosome.

Question 14

What is the role of DNA polymerase III in bacterial DNA replication?

Accepted Answer

It is the main enzyme responsible for elongating new DNA strands.

Question 15

Which equation correctly represents the direction of DNA chain elongation by DNA polymerase?

Accepted Answer

$$5' \rightarrow 3'$$

Question 16

Okazaki fragments are associated with which strand during DNA replication, and how are they joined?

Accepted Answer

Lagging strand; joined by DNA ligase

Question 17

Which activity of DNA polymerase is responsible for proofreading newly synthesized DNA?

Accepted Answer

$$3' \rightarrow 5'$$ exonuclease activity

Question 18

What is the function of primase during DNA replication?

Accepted Answer

It synthesizes short RNA primers to provide a starting point for DNA polymerase.

Question 19

In E. coli, which enzyme removes RNA primers and replaces them with DNA?

Accepted Answer

DNA polymerase I

Question 20

Which of the following best describes the process of theta ($$	heta) $$replication?

Accepted Answer

Bidirectional replication of circular DNA molecules in bacteria

Cell Biology Study Notes: The Nucleus and DNA Replication

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