# DBT JRF 2022 — Question 36

Exam: DBT JRF 2022 · Section: A · Topic: Cell Biology › Histone Proteins & Chromatin · Difficulty: Medium

## Question

Which one of the following acts as a linker histone?

## Options

- **A.** H1
- **B.** H2A
- **C.** H2B
- **D.** H3

## Answer

Option A

## Explanation

H1: The linker histone: Histone H1 is NOT part of the nucleosome core octamer. It functions as the linker histone: • Binds to the DNA that enters and exits the nucleosome (linker DNA, ~20–80 bp between nucleosomes) • Stabilises the nucleosome structure by locking the DNA in place • Essential for compaction of the 10 nm nucleosome 'beads-on-a-string' fibre into the 30 nm chromatin fibre • Each nucleosome has ONE H1 molecule (versus two copies each of H2A, H2B, H3, H4) Functions of core histones: • H3 and H4: form the tetramer that serves as the nucleosome 'reel'; most conserved histones • H2A and H2B: form two dimers that complete the octamer Answer: H1 (Option 1).

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