key term - Histones

Definition

Histones are proteins that package and order DNA into structural units called nucleosomes. They play a crucial role in gene regulation and DNA replication.

5 Must Know Facts For Your Next Test

1. Histones are positively charged, allowing them to bind tightly to the negatively charged DNA.
2. There are five main types of histones: H1, H2A, H2B, H3, and H4.
3. The core histones (H2A, H2B, H3, and H4) form an octamer around which DNA wraps approximately 1.65 times to form a nucleosome.
4. Histone modifications such as methylation and acetylation can influence gene expression by altering chromatin structure.
5. During DNA replication, histones are disassembled and reassembled to ensure proper packaging of newly synthesized DNA.

Review Questions

Related terms

Nucleosome:

The basic unit of DNA packaging consisting of a segment of DNA wound around a core of histone proteins.

Chromatin:

A complex of DNA and protein found in eukaryotic cells that packages long strands of DNA into more compact structures.

Epigenetics:

The study of changes in gene function that do not involve changes in the DNA sequence but are influenced by factors like histone modification.