Difficulty: Easy
Correct Answer: Histone H1
Explanation:
Introduction:
Nucleosomes compact eukaryotic DNA by wrapping it around histone octamers. Beyond the core histones, an additional histone associates with linker DNA between nucleosomes and contributes to chromatin fiber organization and stability.
Given Data / Assumptions:
Concept / Approach:
Histone H1, often called the linker histone, binds near the nucleosomal dyad and contacts linker DNA. This reduces DNA accessibility and promotes formation of higher order fibers, modulating gene regulation by changing chromatin openness.
Step-by-Step Solution:
Verification / Alternative check:
Biophysical studies show that H1 binding compacts arrays into higher order structures. Knockdown experiments increase chromatin accessibility, validating this role.
Why Other Options Are Wrong:
H2A, H2B, H3, and H4 form the core octamer, not the linker binder. CENP A is a centromeric H3 variant specific for kinetochore chromatin, not general linker association.
Common Pitfalls:
Assuming all histones behave identically or confusing H1 with core histones. Another pitfall is equating histone variants with linker function without evidence.
Final Answer:
Histone H1
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