epigenetics Flashcards
nucleus structure
what do the nucleoli contain?
contains:
- rDNA
- rDNA synthesis
- ribosome assembly
chromatin
what are the 2 two types of chromatin?
heterochromatin:
- tightly packed DNA, not transciptionally active
euchromatin:
- less tightly packed, site of active transcription
epigenetic control of gene expression
define epigenetics
- regulartion of gene expression by modifications to the DNA and chromatin structure which do not alter the underlying DNA sequence
DNA methylation
outline what happens to gene transcription when methylation is:
- High
- low
high methylation: less tightly packed chromatins, so transcription factors have more access to sections of DNA so more transcription can occur
low methylation: more tightly packed chromatins, so transcription factors have less access to sections of DNA meaning less transcription occurs
dna methylation
where does cytosine methylation often occur
often occurs at clusters of cytosine-guanine dinucleotides (CpG)
developmental remodelling of DNA methylation
why does the parental methylation patterns in the gametes need to be removed from the developing embryo?
so that the embryonic methylation pattern can be established
non-coding RNAs - micro RNAs
outline X chromosome inactivation
- both X chromosomes in mother have the Xist gene but only one randomly expresses it.
- this Xist is a non-coding RNA, and when expressed it binds on the chromosome all over, recruiting a series of modifications to the DNA.
- this makes the X chromosome expressing this gene highly DNA methylated, shutting down this X chromosome
histone acetylation
what happens to transcription when you have high and low Histone tail acetylation
high histone tail acetylation:
- more open chromatin structure so more transcription
low histone acetylation:
- less open chromatin structure so less transcription
