Chromosome structure.ppt
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The document discusses chromosome structure and compaction. It describes how DNA must be compacted from its full length of around 4 meters into the nucleus that is only about 10 micrometers in diameter. This compaction is achieved through nucleosomes, which involve wrapping DNA around histone proteins to form beads on a string. Specifically, four core histone proteins (H2A, H2B, H3, H4) form an octamer that DNA winds around, while a fifth histone (H1) acts as a linker between nucleosomes. Higher-order compactions beyond the nucleosome level allow the long DNA strands to further fold into the dense chromosome structures found within cells.
Chromosome structure.ppt
- 5. Chromosome structure The DNA compaction problem The nucleosome histones (H2A, H2B, H3, H4) The histone octamere Histone H1 the linker histone Higher order compactions Chromatin loops and scaffolds (SAR)
- 6. Take 4 meters of DNA (string) and compact them into a ball of 10M.– so now walk from here to the main entrance let say 400 meters and try to compact it all into 1 mm.
- 10. Nucleosomes Histone proteins basic (+ charged lysine & arginine) amino acids that bind DNA backbone Four core histones in nucleosome Two of each of H2A, H2B, H3 & H4 Fifth histone, H1 is the linker histone
- 11. Histone amino acids lysine & arginine proteins H1 200-265 27% 2% H2A 129-155 11% 9% H2B 121-148 16% 6% H3 135 10% 15% H4 102 11% 4%
- 12. Nucleosomes
- 15. Compaction level in euchromatin Compaction level in heterochromatin During interphase most chromosomal regions are euchromatic