Question

In tertiary structure of DNA, what is a histone octamer?

• A. A complex consisting of eight positively charged histone proteins (two of each $H_{2}A,H_{2}B,H_3$ and $H_4$) that aid in the packaging of DNA.
• B. A complex consisting of eight negatively charged histone proteins (two of each $H_{2}A,H_{2}B,H_3$ and $H_4$) that aid in the packaging of DNA.
• C. A complex consisting of nine positively charged histone proteins ($H_1$ and two of each $H_{2}A,H_{2}B,H_3$ and $H_4$) that aid in the packaging DNA.
• D. A complex consisting of nine negatively charged histone proteins ($H_1$ and two of each $H_{2}A,H_{2}B,H_3$ and $H_4$) that aid in the packaging of DNA.

Answer 1

The correct option is A A complex consisting of eight positively charged histone proteins (two of each $H_{2}A,H_{2}B,H_3$ and $H_4$) that aid in the packaging of DNA.

A histone octamer is a complex of eight positively charged histone proteins (two of each $H_{2}A,H_{2}B,H_3$ and $H_4$) that aid in the packaging of DNA.

Negatively charged DNA wraps around these histone octamers to form the nucleosome. The DNA is held there by ionic bonds. Linker histone H1 binds to each nucleosome where the DNA enters and exits and this draws a string of nucleosomes closer together to form the 10 nm fibre. The nucleosomes in chromatin are seen as beads-on string structure when viewed under electron microscope.