Question 1

Which statement best explains the 'C value paradox' observed in genetics?

Accepted Answer

The total amount of DNA in the haploid genome (C value) varies widely among species and does not correlate with organismal complexity.

Question 2

In prokaryotes such as E. coli, which two main mechanisms are used to package the genome within the cell?

Accepted Answer

Supercoiling and formation of DNA loops

Question 3

What is the primary function of topoisomerases in both prokaryotic and eukaryotic cells?

Accepted Answer

To break and rejoin DNA strands, relieving tension caused by supercoiling

Question 4

Which of the following best describes a nucleosome?

Accepted Answer

A segment of DNA wrapped twice around a core of eight histone proteins

Question 5

How many base pairs of DNA are typically wrapped around a nucleosome core?

Accepted Answer

$$146$$

Question 6

Which histone is NOT considered a 'core histone' in the nucleosome structure?

Accepted Answer

H1

Question 7

What is the effect of acetylation of histone tails on chromatin structure and gene expression?

Accepted Answer

Chromatin relaxes and genes are expressed.

Question 8

During which phase of the cell cycle does chromatin reach its highest level of condensation?

Accepted Answer

Prophase of mitosis

Question 9

Which of the following best describes the 'beads-on-a-string' form of chromatin?

Accepted Answer

Nucleosomes connected by short stretches of linker DNA

Question 10

If a eukaryotic cell fails to properly regulate histone methylation, what is the most likely consequence?

Accepted Answer

Chromatin will become compact and gene expression will be silenced.

Question 11

Which equation correctly represents the relationship between the number of nucleosomes ($$N) $$and the total number of base pairs ($$B) in a $$DNA segment, assuming each nucleosome wraps 146 base pairs and the average linker DNA is $$L$$ base pairs?

Accepted Answer

$$N = \frac{B}{146 + L}$$

Question 12

Which of the following is a real-world consequence of improper DNA packaging in human cells?

Accepted Answer

Genomic instability leading to cancer

Question 13

Which enzyme is responsible for adding acetyl groups to histone tails, thereby affecting chromatin structure?

Accepted Answer

Histone acetyltransferase

Question 14

A mutation in the gene encoding histone H1 would most likely affect which aspect of chromatin structure?

Accepted Answer

The compaction of nucleosomes into higher-order structures

Question 15

Which of the following best describes the role of 'writer' and 'eraser' enzymes in chromatin regulation?

Accepted Answer

'Writer' enzymes add chemical modifications to histone tails, and 'eraser' enzymes remove them.

Question 16

Which of the following is NOT a function of histone proteins in eukaryotic cells?

Accepted Answer

Catalyzing the synthesis of DNA during replication

Question 17

Which structural feature distinguishes euchromatin from heterochromatin?

Accepted Answer

Euchromatin is less condensed and transcriptionally active.

Question 18

Which of the following best explains why eukaryotic cells require more complex DNA packaging than prokaryotic cells?

Accepted Answer

Eukaryotic genomes are much larger and require multiple levels of compaction to fit within the nucleus.

Question 19

Which of the following statements about linker DNA is correct?

Accepted Answer

Linker DNA connects adjacent nucleosomes and varies in length from about 8 to 80 base pairs.

DNA Packaging in Prokaryotes and Eukaryotes

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