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what is a histone composed of
H3-H4 tetramer, 2 H2A-H2B dimers
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what does histone H1 do
helps the nucleosomal DNA compact
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what is a nucleosome
the histone and the DNA wrapped around it
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what is a chromatin
a group of histones and the DNA wrapped around them
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what does ATP-dependent chromatin-remodeling complexes do
Convert ATP to ADP through hydrolysis to contract or loosen chromatin
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what is a histone fold
three alpha helices
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what is euchromatin
less condensed segments of chromatin that is open and active
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what is heterochromatin
more condensed segments of chromatin that is closed and inactive
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what happens in Position effect variegation
the barrier between euchromatin and heterochromatin is flipped allowing the heterochromatin to spread to the euchromatin
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what effect does Methylation have on the histone
it associates more with the other histones, making it less accessible
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what effect does acetylation have on the histone
it assocates less with other histones making it more accesible
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what does reader protein complexes do
recognize covalent modifications on histones allowing another protein to bind to the reader to enable transcription or r
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how are histone modfications named
histone (H3,H4), amino acid changed (K,G,) placement of amino acid(3,4,5), change, (AC, ME3, ME)
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how does hetrochromatin spread
reader writer complex attaches to heterochromatin and spreads until it reaches barrier DNA
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how is hetrochromatin inherited through epigenetic inheritance
hetrochromatin will stay within the barrier DNA causing it to spread within the barrier DNA forming the same stretch hetrochromatin
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what does HP1 do
causes the histones to gel together
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what does Cohesin do
forms the first loops
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what does Condensin 2 do
makes the loops formed by cohesin larger and larger
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what does condensin 1 do
form loops in the loops formed by cohesin and condensin 2
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what does the sliding clamp do
prevents the DNA polymerase from falling off the DNA
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how does DNA polymerase proofread it's own work
if the nucleotide added is wrong, it will take longer to bind and will instead leave before it's binded, if the wrong one is binded, it will drift to the editing site where it is removed
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what happens when the DNA polymerase finishes the ozaki fragment
leaves, then the previous RNA primer is removed by nucleases and replaced with DNA by repair DNA polymerase
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what does DNA ligase do to okazaki fragments
attaches ATP to the 5 prime phosphate, causing it to leave as AMP and for the 5 prime and 3 prime phosphate to bind together, making a continues loop
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what does DNA helicase do
converts ATP to ADP so it can separate the two strands of DNA
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what does Single-strand DNA-binding proteins do
binds to DNA split by the helicase so it can not form hairpins by binding with itself
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what does DNA polymerase ε(epsilon) do
replication of the leading strand
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what does DNA polymerase α(alpha) aka primase do
makes the RNA primers
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what does DNA polymerase δ(delta) do
replication of the lagging strand
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how does Strand-directed mismatch repair work
MutS protein locks onto a mismatched DNA, then recuits MutL to scan DNA until it reaches a sliding clamp and removes the strand, the strand is then repaired by DNA polymerase delta
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what does DNA topoisomerases
helps relive torsional stress by breaking and reforming bonds
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what is the replication origin
place where DNA is first split because it is AT rich which is weaker
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what happens to histones during replciation
the H3-H4 tetramer attaches equally to the new two strands while the H2A-H2B dimers leave
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what does telomerase do
uses RNA to extend the telomere or ends of the DNA strand
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when does DNA replciation happen
in the S phase
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what does the FACT protein do
takes the H3-H4 proteins from the histones from the DNA being split by the heliocase and places it on to the two new strands of DNA
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