Module 11
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The lowest level of chromosome organisation in a eukaryotic chromosome
nucleosome
A core nucleosome is composed of
two copies each of histone H2A, H2B, H3 and H4
An activator which positively regulates the expression of one or more genes
DNA-binding protein, transcription rates increase when an activator is bound to the DNA
Repressor proteins
Impede access of RNA polymerase to the promoter
The name of the major eukaryotic coactivator consisting of 20 or more polypeptides
mediator
When a regulatory protein represses transcription at specific promoters
Negative regulation
The role of an enhancer in eukaryotic gene transcription is to
Facilitate the expression of a given gene
What is underwound
lesser wound and it is strained
What happens when its underwound,
supercoil forms
What is type I topoisomerase purpose
Cut one strand and turn it to another side, phospahte bind to Tyr in the topoisomerase. covalent linkage, connected with no errors
What is type II topoisomerase
Holding two double stranded DNA, two monomer cutting the C gate and pass it through the other strand.
When does sister chromosome appear
metaphase
What does chromatin contain
1/3 DNA, 2/3 protein by mass
How many protein are in the histones
8
How many types are there in histones
5
Where is histone H1
outside, act as a clip to stabilise it
What are amino tails
from histones, allow the tail to interact with each other. binds to enzyme easier to modify and regulate them
Where does modification occur
histone tails and in the body of the histones
How is it modified
structure and packing of the chromatin access to the DNA of DNA binding proteins
What does histone acetylation do
regulates chromatin condensation, wind by histones deacetylases and unwind by histone acetyl transferases HAT(decondensed chromatin)
What is chromatin remodlling
change section of chromatin for it to move around more. can remove histone, change histone variants, covalent modification of histones(by enzyme) change the accessibility of the DNA
How histone are read
scaffold protein, protein complex with catalytic activities and additional binding site to change the histones usage(modification.
What are the use of histone modification
Silencing genes, change expression, dna repair
When was chromatin more condensed
In mitosis