Part 3: DNA Packaging in Prokaryotes and Eukaryotes (25 MCQs)
Part 3: DNA Packaging in Prokaryotes and Eukaryotes (25 MCQs)
Q51. In prokaryotes, DNA is organized into:
a) Chromatin
b) Chromosomes with histones
c) Nucleoid without histones
d) Nucleus
Answer: c
- c) Correct: Prokaryotes (like bacteria) have nucleoid region without histones.
- a, b, d) Found in eukaryotes.
Q52. In eukaryotes, DNA is wrapped around:
a) Ribosomes
b) Histone proteins
c) Lipids
d) RNA molecules
Answer: b
- b) Correct: DNA wraps around histones (H2A, H2B, H3, H4) to form nucleosomes.
Q53. The basic unit of DNA packaging in eukaryotes is:
a) Chromosome
b) Gene
c) Nucleosome
d) Chromatin
Answer: c
- c) Correct: Nucleosome = DNA + histone octamer.
Q54. How many base pairs of DNA are wrapped around histone octamer in a nucleosome?
a) 146 bp
b) 100 bp
c) 300 bp
d) 500 bp
Answer: a
- a) Correct: 146 bp DNA wraps around histone core.
Q55. Linker DNA between nucleosomes is associated with:
a) H2A
b) H1
c) H3
d) H4
Answer: b
- b) Correct: H1 histone binds linker DNA, stabilizing nucleosome.
Q56. Histone proteins are rich in:
a) Acidic amino acids
b) Basic amino acids
c) Neutral amino acids
d) Sulfur-containing amino acids
Answer: b
- b) Correct: Histones rich in lysine & arginine (basic) → bind negatively charged DNA.
Q57. The nucleosome model of chromatin was proposed by:
a) Watson and Crick
b) Kornberg
c) Hershey and Chase
d) Franklin
Answer: b
- b) Correct: Roger Kornberg proposed nucleosome model.
Q58. Chromatin is made of:
a) DNA only
b) DNA and RNA
c) DNA and proteins
d) Only histones
Answer: c
- c) Correct: Chromatin = DNA + histone & non-histone proteins.
Q59. Euchromatin is characterized by:
a) Densely packed, inactive
b) Loosely packed, active
c) No genes
d) Found only in bacteria
Answer: b
- b) Correct: Euchromatin = loosely packed, transcriptionally active.
Q60. Heterochromatin is:
a) Loosely packed and active
b) Densely packed and inactive
c) DNA without proteins
d) Found only in prokaryotes
Answer: b
- b) Correct: Heterochromatin = condensed, transcriptionally inactive.
Q61. Beads-on-a-string structure refers to:
a) Nucleosome arrangement
b) Chromosome metaphase shape
c) DNA helix
d) Ribosome structure
Answer: a
- a) Correct: Nucleosomes connected by linker DNA look like beads-on-a-string.
Q62. Higher-level chromatin structure forms:
a) Nucleoid
b) Loops and solenoid fibers
c) Ribosomes
d) Mitochondria
Answer: b
- b) Correct: Nucleosomes coil into solenoid fibers (30 nm fiber) and higher loops.
Q63. The human haploid genome has approximately:
a) 3 × 10⁶ bp
b) 3 × 10⁹ bp
c) 6 × 10⁹ bp
d) 1 × 10⁶ bp
Answer: b
- b) Correct: Human haploid genome ≈ 3 billion base pairs.
Q64. Human diploid genome contains about how many genes?
a) 3,000
b) 30,000
c) 300,000
d) 3 million
Answer: b
- b) Correct: Around 30,000–35,000 genes in humans.
Q65. Packaging ratio of DNA in nucleosome is about:
a) 2-fold
b) 7-fold
c) 20-fold
d) 100-fold
Answer: b
- b) Correct: Nucleosome provides ~7-fold compaction.
Q66. Metaphase chromosome compaction is approximately:
a) 10-fold
b) 100-fold
c) 10,000-fold
d) 1,000-fold
Answer: c
- c) Correct: Final compaction at metaphase ≈ 10,000-fold.
Q67. The centromere is attached to:
a) Spindle fibers
b) Chromosome arms
c) Ribosomes
d) DNA polymerase
Answer: a
- a) Correct: Centromere = site of spindle attachment during division.
Q68. Telomeres are composed of:
a) Repetitive DNA sequences
b) Histones only
c) RNA only
d) Enzymes
Answer: a
- a) Correct: Telomeres = repetitive non-coding DNA (TTAGGG in humans).
Q69. The enzyme maintaining telomere length is:
a) DNA polymerase
b) Telomerase
c) Helicase
d) Ligase
Answer: b
- b) Correct: Telomerase adds repeats to chromosome ends.
Q70. Non-histone proteins in chromatin function mainly in:
a) DNA replication and regulation
b) Base pairing
c) Hydrogen bonding
d) Protein folding
Answer: a
- a) Correct: Non-histone proteins regulate replication, transcription.
Q71. The scaffold of metaphase chromosome is made of:
a) Only histones
b) Non-histone proteins
c) DNA only
d) RNA
Answer: b
- b) Correct: Scaffold = non-histone proteins giving structure.
Q72. Nucleosome core contains how many histone molecules?
a) 2
b) 4
c) 6
d) 8
Answer: d
- d) Correct: Octamer = 2 each of H2A, H2B, H3, H4 → 8 histones.
Q73. H1 histone differs from core histones because:
a) It is acidic
b) It binds linker DNA
c) It pairs with bases
d) It is absent in nucleosomes
Answer: b
- b) Correct: H1 stabilizes DNA outside core → linker histone.
Q74. Chromatin during interphase exists as:
a) Euchromatin and heterochromatin
b) Nucleoid only
c) Ribosome clusters
d) Mitochondria
Answer: a
- a) Correct: Chromatin = euchromatin (active) + heterochromatin (inactive).
Q75. Which of the following is correct about nucleosome?
a) DNA wraps around histone octamer
b) Core has 146 bp DNA
c) Linker DNA bound by H1
d) All of the above
Answer: d
- d) Correct: All statements describe nucleosome structure.
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