Free Chromosomes MCQs with Answers
633 Chromosomes MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Chromosomes are DNA-protein structures that carry genes and become visible during cell division. Coverage includes chromatin, centromeres, sister chromatids, homologous chromosomes, chromosome number, and the distinction between diploid and haploid cells, with links to DNA replication, mitosis and meiosis.
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- A. Peptidyl transferase reaction
- B. Aminoacyl tRNA binding to A-site
- C. Translocation
- D. Amino acid activation
Explanation: ATP/GTP is consumed during amino acid activation, tRNA binding, and translocation.
Correct answer: Peptidyl transferase reaction- A. AGT, TAG, UGA
- B. UAG, UGA, UAA
- C. TAG, TAA, TGA
- D. GAT, AAT, AGT
Explanation: The genetic code contains three stop codons: UAG, UAA, and UGA. These terminate translation and are called nonsense codons.
Correct answer: UAG, UGA, UAA- A. AT-GC
- B. AG-CT
- C. AC-GT
- D. All of these
Explanation: Base pairing in DNA follows Chargaff's rule: A pairs with T and G pairs with C.
Correct answer: AT-GC- A. Inhibitor
- B. Repressor
- C. Regulator
- D. All of these
Explanation: In the operon model, the regulator gene codes for a (repressor) protein that controls the expression of the operon.
Correct answer: All of these- A. Dispersive
- B. Conservative
- C. Semi-conservative
- D. Non-conservative
Explanation: Each daughter DNA molecule has one parental and one newly synthesized strand (Meselson-Stahl experiment).
Correct answer: Semi-conservative- A. 5' ➡ 3'
- B. 3' ➡ 5'
- C. Both (A) and (B)
- D. Any
Explanation: RNA polymerase always synthesizes RNA in the 5′ → 3′ direction, using the template strand in the 3′ → 5′ direction.
Correct answer: 5' ➡ 3'- A. Single form
- B. Tetrad form
- C. Pair form
- D. Identical form
Explanation: Diploid organisms carry chromosomes in homologous pairs, one from each parent, carrying same genes but possibly different alleles.
Correct answer: Pair form- A. 10 nucleotides/ sec
- B. 1000 nucleotides/ sec
- C. 100 nucleotides/ sec
- D. 10000 nucleotides/ sec
Explanation: DNA polymerase III adds nucleotides rapidly (~1000/sec) during prokaryotic replication.
Correct answer: 1000 nucleotides/ sec- A. DNA ligase
- B. DNA topoisomerase I
- C. DNA gyrase
- D. Helicase
Explanation: Helicase unwinds the DNA double helix by breaking hydrogen bonds, providing single-stranded templates.
Correct answer: Helicase- A. Multi-helix stage
- B. Single-helix stage
- C. Double -helix stage
- D. None of these
Explanation: X-ray crystallography and radiotracers confirmed DNA's double-helical structure held by complementary base pairing.
Correct answer: Double -helix stage- A. 5-bromouracil
- B. 5-methylcytosine
- C. Guanine
- D. Adenine
Explanation: Spontaneous deamination of 5-methylcytosine creates thymine (C→ T), making CpG sites mutation "hot spots."
Correct answer: 5-methylcytosine- A. RNA polymerase
- B. RNA primase
- C. RNA ligase
- D. RNA protease
Explanation: RNA ligase seals exons after introns are removed, producing a continuous coding sequence.
Correct answer: RNA ligase- A. L-shaped
- B. S-shaped
- C. Y-shaped
- D. E-shaped
Explanation: tRNA folds into an L-shape in 3D, fitting correctly into ribosomes during translation.
Correct answer: L-shaped- A. Formation of formyl-met-tRNA
- B. Binding of 30S subunit of ribosome with mRNA
- C. Association of 30S-mRNA with formyl-met-tRNA
- D. Association of 50S subunit of ribosome with initiation complex
Explanation: In prokaryotic translation initiation, a GTP molecule is required for the step where the 50S ribosomal subunit joins the 30S initiation…
Correct answer: Association of 50S subunit of ribosome with initiation complex- A. On plates with and without streptomycin
- B. On plates with minimal medium
- C. Only on plates with streptomycin
- D. Only on plates without streptomycin
Explanation: Imprints on both plates (with and without streptomycin) help identify streptomycin-resistant mutants by comparing growth patterns.
Correct answer: Only on plates with streptomycin- A. One DNA strand with another
- B. One nucleoside with another
- C. One nucleotide with another nucleotide
- D. One nitrogenous base with a pentose sugar
Explanation: Phosphodiester bonds connect 3′-OH of one sugar with 5′ phosphate of next nucleotide, forming the DNA backbone.
Correct answer: One nucleotide with another nucleotide- A. Codes for enzymes needed for DNA replication
- B. Codes for protein needed in cell cycle
- C. Does not code for proteins and is same in all members of population
- D. Shows high polymorphism in the population and is inherited
Explanation: Satellite DNA varies greatly among individuals. Its polymorphism is used in DNA fingerprinting, paternity tests, and forensic studies.
Correct answer: Shows high polymorphism in the population and is inherited- A. Centromere
- B. Chromatid
- C. Telomere
- D. Kinetochore
Explanation: The centromere is the constricted region joining the two sister chromatids and is essential for spindle attachment during cell division.
Correct answer: Centromere- A. Sugar-phosphate backbone
- B. Nitrogenous base
- C. Nucleotides
- D. Hydrogen bonds
Explanation: The sugar-phosphate backbone of DNA is formed by alternating deoxyribose sugar and phosphate groups linked by phosphodiester bonds.
Correct answer: Sugar-phosphate backbone- A. Sister Chromatid
- B. Centromere
- C. Chromatin
- D. Telomere
Explanation: The label X points to the tip (end) of the chromatid arm. Telomeres are the protective caps at the ends of chromosomes that prevent…
Correct answer: Telomere