Human chromosome structure MCQs With Answer

Introduction

This quiz set on “Human chromosome structure MCQs With Answer” is designed specifically for M.Pharm students studying Advanced Pharmaceutical Biotechnology. It focuses on the molecular architecture of chromosomes, chromatin organization, centromeres and telomeres, histone composition, higher-order folding, epigenetic marks, chromosomal abnormalities and the proteins that regulate chromosome dynamics. Questions progress from core structural units to functional consequences relevant to replication, transcription regulation, and genome stability — topics essential for understanding drug targets, toxicogenomics, and genomic medicine applications in pharmaceutics. Each MCQ includes four options and a clear answer to help reinforce learning, prepare for exams, and support deeper conceptual understanding.

Q1. What is the fundamental repeating unit of chromatin responsible for packaging DNA into nucleosomes?

• Nucleosome
• Solenoid
• Chromatosome
• Histone fold domain

Correct Answer: Nucleosome

Q2. Which set of histone proteins forms the core octamer around which DNA is wrapped in a nucleosome?

• H1 only
• H2A, H2B, H3 and H4
• H1 and H5
• H2A and H3 only

Correct Answer: H2A, H2B, H3 and H4

Q3. Approximately how many base pairs of DNA are wrapped around the histone octamer in the core nucleosome?

• 50–60 bp
• 147 bp
• 300 bp
• 1000 bp

Correct Answer: 147 bp

Q4. Which histone is primarily known as the linker histone that helps stabilize higher-order chromatin folding?

• H2A
• H3
• H1
• H4

Correct Answer: H1

Q5. Which structural model describes the 30-nm chromatin fiber formed by coiling of nucleosome arrays and is stabilized by H1?

• Beads-on-a-string model
• Solenoid model
• Zigzag model
• Alpha helix model

Correct Answer: Solenoid model

Q6. Human centromeric DNA is primarily composed of which repetitive sequence family?

• Telomeric repeats (TTAGGG)
• Alpha-satellite repeats
• LINE-1 elements
• SINE/Alu repeats

Correct Answer: Alpha-satellite repeats

Q7. What is the canonical hexanucleotide repeat sequence found at human telomeres?

• CGGCGG
• TTAGGG
• AATTTT
• GAACTC

Correct Answer: TTAGGG

Q8. Which enzymatic activity is responsible for adding telomeric repeats to chromosome ends in germline and many cancer cells?

• DNA polymerase δ
• Telomerase (ribonucleoprotein reverse transcriptase)
• Topoisomerase II
• Exonuclease I

Correct Answer: Telomerase (ribonucleoprotein reverse transcriptase)

Q9. Which protein complex mediates sister chromatid cohesion from S phase until anaphase?

• Condensin
• Cohesin
• ORC (Origin Recognition Complex)
• SWI/SNF chromatin remodeler

Correct Answer: Cohesin

Q10. Which complex is primarily responsible for mitotic chromosome condensation?

• Cohesin
• Condensin
• Telomerase
• RNA polymerase II

Correct Answer: Condensin

Q11. Constitutive heterochromatin is best described by which combination of features?

• Gene-rich, transcriptionally active, early-replicating
• Highly repetitive, transcriptionally silent, late-replicating
• Single-copy sequences, high GC content, CpG islands
• Sites of frequent recombination and high gene expression

Correct Answer: Highly repetitive, transcriptionally silent, late-replicating

Q12. Euchromatin is characterized by which of the following?

• Dense packing, enriched H3K9me3, transcriptional silence
• Open chromatin, gene-rich, transcriptionally active
• Only found at centromeres
• Composed entirely of satellite DNA

Correct Answer: Open chromatin, gene-rich, transcriptionally active

Q13. A Robertsonian translocation typically involves fusion between which types of human chromosomes?

• Two metacentric chromosomes fusing at telomeres
• Two acrocentric chromosomes fusing at or near the centromere (long arms)
• Sex chromosomes only (X and Y)
• Small inversions within a single chromosome arm

Correct Answer: Two acrocentric chromosomes fusing at or near the centromere (long arms)

Q14. The Fragile X syndrome molecular lesion is primarily caused by expansion of which trinucleotide repeat in the FMR1 gene?

• CAG repeat expansion
• CGG repeat expansion
• GAA repeat expansion
• CTG repeat expansion

Correct Answer: CGG repeat expansion

Q15. The C-value paradox (variation in genome size not correlating with organismal complexity) is largely explained by what?

• Differences in coding gene number only
• Abundance of noncoding and repetitive DNA sequences
• Errors in genome sequencing technology
• Variation in chromosome centromere structure

Correct Answer: Abundance of noncoding and repetitive DNA sequences

Q16. Which chromosome banding technique uses trypsin digestion followed by Giemsa staining and is standard for human karyotyping?

• R-banding
• Q-banding
• G-banding (Giemsa after trypsin)
• C-banding

Correct Answer: G-banding (Giemsa after trypsin)

Q17. Topologically associating domains (TADs) refer to which of the following?

• Linear stretches of DNA that never interact with each other
• Self-interacting genomic regions with frequent intradomain contacts
• Centromeric satellite arrays only
• Telomeric overhang structures

Correct Answer: Self-interacting genomic regions with frequent intradomain contacts

Q18. Lamin-associated domains (LADs) are genomic regions typically associated with which nuclear feature and outcome?

• Nuclear pores and high transcriptional activity
• Nuclear lamina and transcriptional repression
• Centromeres and recombination hotspots
• Replication origins with early S-phase firing

Correct Answer: Nuclear lamina and transcriptional repression

Q19. Telomerase is a ribonucleoprotein with which essential components?

• TERT protein and TERC RNA template
• DNA polymerase α and primase subunit
• Topoisomerase I and II
• RNA polymerase I subunits

Correct Answer: TERT protein and TERC RNA template

Q20. Which complex recognizes origins of replication and is essential for pre-replicative complex formation in eukaryotic chromosomes?

• RFC clamp loader
• Origin Recognition Complex (ORC)
• PCNA sliding clamp
• DNA ligase I

Correct Answer: Origin Recognition Complex (ORC)

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