Question 1

Which of the following best explains why the melting temperature ($T_m$) of DNA increases with higher GC content?

Accepted Answer

GC pairs form three hydrogen bonds, making the DNA more resistant to denaturation.

Question 2

A newly discovered bacterium has a GC content of 48%. According to Chargaff’s rules, what is the percentage of adenine in its DNA?

Accepted Answer

24%

Question 3

Which structural feature distinguishes eukaryotic nuclear chromosomes from bacterial chromosomes?

Accepted Answer

Eukaryotic chromosomes are linear and complexed with histones, while bacterial chromosomes are often circular and complexed with small basic proteins.

Question 4

Which of the following is NOT a function of the nuclear lamina?

Accepted Answer

Facilitating the transport of mRNA through nuclear pores

Question 5

A mutation in the lamin A gene is most likely to affect which cellular structure?

Accepted Answer

Nuclear lamina

Question 6

Which of the following statements about nucleosomes is correct?

Accepted Answer

A nucleosome core particle consists of a histone octamer and 146 base pairs of DNA.

Question 7

Which process is facilitated by the presence of nuclear localization signals (NLS) on proteins?

Accepted Answer

Import of proteins into the nucleus via nuclear pore complexes

Question 8

Which of the following modifications to histone tails is most associated with transcriptionally active chromatin?

Accepted Answer

Acetylation by histone acetyltransferase (HAT)

Question 9

Which of the following best describes the difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and often transcriptionally inactive.

Question 10

Which of the following is true regarding mitochondrial and chloroplast genomes?

Accepted Answer

They are usually circular and lack histones.

Question 11

Which of the following best describes the role of importin in nuclear transport?

Accepted Answer

Importin binds to proteins with NLS and facilitates their transport into the nucleus.

Question 12

Which of the following statements about DNA denaturation is correct?

Accepted Answer

DNA denaturation can be induced by increasing temperature or pH, resulting in strand separation.

Question 13

Which of the following is a correct sequence of events for nuclear import via the Ran/importin pathway?

Accepted Answer

Importin binds to NLS-containing protein in the cytoplasm, transports it through the nuclear pore, releases it in the nucleus, and is recycled back to the cytoplasm.

Question 14

Which of the following is a consequence of histone deacetylation?

Accepted Answer

Chromatin becomes more compact and transcriptionally inactive.

Question 15

Which of the following statements about the structure of the DNA double helix is correct?

Accepted Answer

The sugar-phosphate backbone is on the outside, and the nitrogenous bases are on the inside forming base pairs.

Question 16

Which of the following is true about the packaging of eukaryotic DNA?

Accepted Answer

Histone H1 facilitates the conversion of the 10-nm fiber to the 30-nm fiber.

Question 17

Which of the following is a function of constitutive heterochromatin?

Accepted Answer

It serves structural functions within chromosomes, such as centromeres and telomeres.

Question 18

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

Accepted Answer

NPCs are composed of nucleoporin proteins and facilitate transport between the cytoplasm and nucleoplasm.

Question 19

Which of the following best describes the role of nuclear export signals (NES)?

Accepted Answer

NES sequences target proteins and RNAs for export from the nucleus via exportins.

DNA, Chromosomes, and the Nucleus: Structure, Packaging, and Function

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