what protein acetylates histones and which reverses acetylation of histione?
histone acetylase and HDAC
what does histone acetylation do to DNA?
makes the interaction weaker and promotes transcription
what does histion methylation do usually to DNA?
increased packaging and decreased transcription
what are the proteins that methylate and demethylate histones?
histone methyl transferases and histone demethylases
how does methylation of histones induce tighter packing of DNA?
binds hetero chromatin protein 1 (HP1) which makes histones cluster and pack DNA tighter
HP1 can bind to lamin B receptor (LBR) and this targets methylated histones to nuclear lamina which has HDACs which deacetylated the histones
where are HDACs located
in nuclear lamina
how was it shown on SDS page that H1 contributes to 30 nm fiber stage of chromatin?
run 30nm fibers on gel and isolate band that is the H1, then extract H1 with low salt buffer and run gel again and there is no band corresponding to H1. (low salt buffer makes chromatin become beads on a string?)
besides SDS PAGE how else was it shown that H1 induces 30nm fiber of chromatin?
with EM, after low salt extraction it was seen that 30nm fiber turned into beads-on-a-string and after adding back H1 the chormatin reverted by to 30nm fibers
how many times is DNA copied in the cell cycle?
just once; in the s-phase
what is semi-conservative replication mean?
forms a hybrid between daughter strand and parent strand
where does replication begin on a chromosome?
about how many oris per bp?
how long does S-phase take in somatic cells
6-10 hours, long compared to embryonic cells (~10 mins) because replication doesn't happen all at once
what are 6 things needed for normal replication?
idenify places on chromosome where rep should start
cell decides its time to start
cell separates dna
recruitment of DNA pol
copying of DNA
link pieces of DNA together
how many bp in an ori approximately?
what is Orc and what does it do?
ori complex; 6 proteins that mark where replication should start
which proteins are activated when the cell judges it is time to begin replication?
Cdt1 and Cdc6 (cell dependent transcript 1) and (cell division cycle 6)
what do active Cdt1 and Cdc6 do?
bind to Orc and MCM complex
what activity does MCM complex have when active?
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