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Genome Organization - Coggle Diagram
Genome Organization
Beads on string structure
primary level of DNA packaging
often called as 11nm fibre
diameter of beads is 11nm
made of protein called as
histones
five major class
H1, H2A, H2B, H3, H4
H1
is present in half the amount of the other four histones
amino acids sequences
H3
and
H4
are highly conserved
rich in basic amino acids:
Arginine
and
Lysine
histone and DNA along with form a condense structure called
nucleosome
it is basic protein but also contain hydrophobic and acid patches. they repel each other at physiological pH and form non-nucleosomal aggregates with DNA
histone chaperons prevent these nonspecific interactions and can direct the production assembly and disassembly of nucleosomes by facilitating histone deposition and exchange
Chromosome formation
metaphase chromosome have
two arm and seperate by centromere
centromere
telomeres
metaphase chromosome
two multiprotein complex help to form metaphase chromosome
condensin and cohesin
packaging of DNA in interphase vs m phase
300 nm radial loop- euchromatin
G1,S,G2 phase
700 nm-heterochromatin
start m phase
Chromatin to Euchromatin and Heterochromatin
Chromatin
Heterochromatin
condensed and inactive
Transcriptionally inactive
Tightly compacted regions of chromosomes
Radial loop domains compacted even further
high DNA density
darkly stained under nuclear stains
found only in eukaryotes
constitutive and facultative
heterochromatin
Euchromatin
Transcriptionally active
uncoiled and active
Less condensed regions of chromosomes
Regions where 30 nm fiber forms radial loop domains
low DNA density
lightly stained under nuclear stains
found in both prokaryotes and eukaryotes
constitutive euchromatin
Nucleosome to chromatin fibre
chrosmatosome ( nucleosome + H1 Histone) condensed to form 30nm fiber in spiral orientation
Solenoid Model
also referred as "one start model"
feature:
nucleosomes follow each other along the same helical path
interaction between the histones core occur sequently
Zig zag Model
considered as " two start model" which is indicate by two different colours of histone cores
Yellow: interacting nucleosome partner (1,3,etc)
Violet: nucleosome row (2,4 etc)
linker DNA connects two opposing nucleosomes, creating a structure where the alternate histone cores became interacting partners
