BIOL 200 Lecture Notes - Lecture 13: Cell Nucleus, Interphase, Heterochromatin
Document Summary
Challenges: chromatin needs to be functionally organized, chromatin territories, ordered functional regions in the interphase nucleus, heterochromatin and euchromatin. Heterochromatin: tightly packed form of dna (more densely packaged); abundant in cells that are less active or not active. Euchromatin: dispersed and not readily stainable; prevalent in cells that are active in transcription. Concentrated around centromere and being transcribed. telomeres of chromosomes. Not many active genes included in heterochromatin. Note: euchromatin and heterochromatin are not always static. Some regions can change based on the needs of the cell. Levels of dna packing in the nucleus: naked dna, (cid:862)beads o(cid:374) a stri(cid:374)g(cid:863) for(cid:373) of dna. Levels of dna pa(cid:272)kagi(cid:374)g: (cid:862)beads o(cid:374) a stri(cid:374)g(cid:863) Aka nucleosomes, 11nm fiber, type a fiber. Nucleosomes (10-11nm) = dna + core histone proteins (2x h2a, h2b, h3, h4) Interphase chromatin (30nm) can form high-ordered loops of the 30nm fiber.
