Question

Histone octamere contains

• A. 8 types of histones
• B. 5 types of histones
• C. 6 types of histones
• D. 8 histones of four different types

Hint:

Do not confuse the total number of histones in the octamer with the number of types.
Total count = 8 proteins (hence "octamer").
Distinct types = 4 (H2A, H2B, H3, H4), occurring as dimers.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Eukaryotic genomic DNA is packaged into a highly organized structure called chromatin.
The basic repeating structural unit of chromatin is the nucleosome.

Step 2: Detailed Explanation:
A nucleosome is composed of a segment of DNA wrapped around a protein core known as the histone octamer.
The histone octamer consists of eight individual histone proteins.
These eight proteins are composed of two copies each of four distinct core histone types:
- Histone H2A (two molecules)
- Histone H2B (two molecules)
- Histone H3 (two molecules)
- Histone H4 (two molecules)
Together, these four types form a central disk-like protein core.
Approximately 147 base pairs of double-stranded DNA wrap around this octamer core 1.65 times.
Histone H1 is a linker histone that sits outside the core particle and is not a component of the octamer.
Thus, the octamer consists of 8 histones representing 4 distinct types.

Step 3: Final Answer:
The histone octamer contains 8 histones of four different types.