Question

How does DNA fold into a chromosome. What are the 6 steps

Answer 1

The essential unit of DNA packaging is the nucleosome. A nucleosome consists of a small amount of DNA wrapped up with protein. The proteins that interact with DNA to form chromatin comprise a family of basic (positively charged) proteins called histones. There are five different types of histone protein: H1, H2A, H2B, H3, and H4. Of these, two molecules each of H2A, H2B, H3, and H4 combine to form a histone octamer. DNA wraps around the octamer, making 1 3/4 turns around the protein complex. The amount of DNA associated with the histone octamer is 146 bp. The octamer plus the DNA comprise what is called the nucleosome core. A small stretch of DNA (60 bp) runs between adjacent nucleosome cores, and is known as the linker. A single nucleosome consists of one core plus a linker. The total amount of DNA involved in a single nucleosome is approximately 206 bp. Chromatin therefore consists of DNA wrapped around one histone octamer after another, like a long string of beads.