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chromosome structure and packaging (DNA packaging (chromosome scaffold (in…
chromosome structure and packaging
DNA packaging
chromatin
H1 binds between linker DNA and NS, 30 nm
chromatin finer , solenoid or zigzag model
chromosome scaffold
in loops 50K-200K bp in 30nm finer, hold in Lampbrush chromosome
chromatins attached to scaffold at SARs/MARs(condensins,topoisomerase2)
relaxed loop & condensed loop
nucleosome
146 bp of DNA IN 1.65 times
100-200 a.a octameric core, linker DNA between 2 NS
11nm
condensin
(chesin)
is thought to encircle sister chromatids
(condensin)
use ATP to maintain the supercoiled loops of DNA
Chromatin Remodelling
: adjustment of nucleosome position in chromatin
ATP-dependent nucleosome remodelling complexes
steps
promoter is accessible to RNA polymerase 2
nucleosome sliding
histone replacement
histone eviction
modification of nucleosome position by sliding DNA strands
recruitment of nucleosome remodelling complexes
transcriptional activators bind to DNA site
modified DNA
modified histones
transcription factors
Histone acetyltransferase
Chromosome Structure
telomeres
function
ensure complete DNA replication
chromosome positioning
maintains structural integrity
werner syndrome
sub-telomere
multigene
pseudogenes
centromere
positions
telocentric
acrocentric
metacentric
submetacentric
karyotype