Question

Histones are organized to form a unit of:

• A. 2 Molecules
• B. 4 Molecules
• C. 6 Molecules
• D. 8 Molecules

Answer 1

Answer:

D. 8 Molecules

• Histones are basic proteins found in eukaryotic cells that package and order DNA into structural units called nucleosomes.
• A nucleosome, the fundamental structural unit of chromatin, consists of a core particle around which DNA is wrapped.
• The histone core particle is composed of eight histone proteins: two copies each of H2A, H2B, H3, and H4. This assembly of eight histone molecules is referred to as an **octamer**.
• The DNA double helix wraps approximately 1.65 times around this histone octamer, forming a nucleosome core.
• This structure is crucial for the compaction of the vast length of DNA within the nucleus of a cell.
• Each DNA-protein unit formed by a nucleosome and its associated linker DNA is called a nucleosome filament or string of beads.
• In terms of competitive exams, understanding the composition of the nucleosome, particularly the number and types of histone proteins involved, is frequently tested.
• The term 'histone' originates from their isolation with the nucleus, first described by Albrecht Kossel in 1884.
• Histones play a vital role in gene regulation by influencing DNA accessibility to transcription factors and other regulatory proteins.