$$\text{Genome size} \propto \text{Organism complexity}$$

Question 1

Which experiment provided the first evidence that DNA is the genetic material, and what was the key result?

Accepted Answer

Griffith's experiment with mice, where heat-killed pathogenic bacteria transformed harmless bacteria into pathogens.

Question 2

Given the DNA strand 5'-GCTA-3', what is the sequence and direction of its complementary strand?

Accepted Answer

3'-CGAT-5'

Question 3

Which molecule is NOT directly involved in the Central Dogma of molecular biology?

Accepted Answer

Lipid

Question 4

What is the chemical difference between ribose and deoxyribose, and why is it significant?

Accepted Answer

Deoxyribose lacks a 2' hydroxyl group, making DNA more chemically stable than RNA.

Question 5

Which base pair is more stable and why?

Accepted Answer

G-C, because it forms three hydrogen bonds.

Question 6

What is the equation for the number of base pairs per helical turn in B-form DNA?

Accepted Answer

$$n = 10$$

Question 7

Which bond connects nucleotide subunits within a DNA strand?

Accepted Answer

Phosphodiester bond

Question 8

If a histone tail is acetylated, what effect does this have on DNA compaction?

Accepted Answer

It neutralizes the positive charge, loosening DNA binding.

Question 9

Which of the following best describes euchromatin?

Accepted Answer

Loosely packed, transcriptionally active chromatin.

Question 10

Why are calico cats almost always female?

Accepted Answer

Because X chromosome inactivation leads to mosaic expression of coat color genes.

Question 11

Which histone is required for the formation of the 30 nm fiber in chromatin?

Accepted Answer

H1

Question 12

What is the composition of a nucleosome core particle?

Accepted Answer

Two each of H2A, H2B, H3, and H4 histones plus ~146 bp of DNA.

Question 13

Which equation represents the directionality of DNA synthesis?

Accepted Answer

$$5' \rightarrow 3'$$

Question 14

What is the main difference between prokaryotic and eukaryotic DNA compaction?

Accepted Answer

Eukaryotes use histones and nucleosomes for compaction; prokaryotes do not.

Question 15

Which process is responsible for the formation of heterochromatin on one X chromosome in female mammals?

Accepted Answer

Histone tail methylation

Question 16

What is the function of chromatin-remodeling complexes?

Accepted Answer

They reposition DNA wrapped around nucleosomes to regulate gene expression.

Question 17

Which equation best describes the relationship between genome size and organism complexity?

Accepted Answer

$$	ext{Genome size} \propto 	ext{Organism complexity}$$

Question 18

Which of the following is NOT a component of a nucleotide?

Accepted Answer

Amino acid

Question 19

What is the effect of trimethylation of lysine residues on histone tails?

Accepted Answer

It promotes heterochromatin formation and gene silencing.

Question 20

Which equation represents the compaction of DNA into chromosomes?

Accepted Answer

$$	ext{DNA strand} ightarrow 	ext{Nucleosome} ightarrow 	ext{30 nm fiber} ightarrow 	ext{Looped domains} ightarrow 	ext{Chromatid}$$

DNA and Chromosomes: Structure, Function, and Organization

Study Guide - Practice Questions