1 DNA Packaging in Chromatin & Chromosomes Packing Ratio Model Naked DNA 20A dia. 10 bp/turn 1 good Chromatin 100A dia. ~80 bp/turn 6-7 good (100 A fiber) Chromatin 300A dia. 6 ν, 1200 bp/turn ~40 vague (300 A fiber) Domains (loops) 20-100 kb/loop ~700 vague Chomosome 10[6] - 10[8] bp ~10,000 defined Electron Micrograph of Chromatin Fibers (rat thymus nucleus) Olins et. al., J. Cell Biol, (1975) 64, 528-537 0.1 μm
14
Embed
DNA Packaging in Chromatin & Chromosomes · 1 DNA Packaging in Chromatin & Chromosomes Packing Ratio Model Naked DNA 20A dia. 10 bp/turn 1 good Chromatin 100A dia. ~80 bp/turn 6-7
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
DNA Packaging in Chromatin & Chromosomes
Packing Ratio ModelNaked DNA 20A dia. 10 bp/turn 1 good
Chromatin 100A dia. ~80 bp/turn 6-7 good(100 A fiber)
Electron Micrograph of Chromatin Fibers (rat thymus nucleus)
Olins et. al., J. Cell Biol, (1975) 64, 528-537
0.1 µm
2
Chromatin Structure
Griffiths et.al. Introduction to Genetic Analysis, 2000
Metaphase Chromosomes Appear to BeOrganized in Domains
Laemmli et. al., 1978
3
Chromosome condensation duringspermatogenesis suggests clustering of adjacent
domains in “rosettes”
Hamkalo et. al., 1978
One Model of Chromosome Organization
Griffiths et.al., Introduction to Genetic Analysis, 2000
4
Electron Micrograph of Chromatin Fibers(rat thymus nucleus)
Olins et. al., J. Cell Biol, (1975) 64, 528-537
0.1 µm
- Anonymous review of paper submitted by C.F.L.Woodcock, 1973, showing EM pictures ofnucleosome arrays
“A eukaryotic chromosome made out of self-assembling 70A units, which could perhaps bemade to crystallize, would necessitate rewritingour basic textbooks on cytology and genetics! Ihave never read such a naïve paper purporting tobe of such fundamental significance. Definitely itshould not be published anywhere!”
5
From “The Microscope Made Easy” by Henry Baker, 1742
CHAP. XV: Cautions in viewing Objects.“Beware of determining and declaring yourOpinion suddenly on any Object, for Imaginationoften gets the Start of Judgment…. Pass noJudgment upon Things over-extended by Force,or contracted by Dryness, or in any Manner out oftheir natural State, without making suitableAllowances.”
Establishing the nucleosome model..- a paradigm shift, 1973-1974