LECTURE 6 (epigenetics and development) Flashcards
What’s epigenetics?
modify the expression of certain genes normally down regulating, this is done w/o changing nt seq
Does epigenetic usually down regulate or up regulate genes?
downregulate
By which two ways can epigenetics act w/o changing the nt seq?
by altering histones or by modifying gene expression (expression of genes that do not involve changes in nt seq=
In which two forms in chromatin present?
Euchromatine: uncondensed express genes
heterochromatin: condensed form transcriptionally silent near centromeres inactive
What are ES cells?
embryonic stem cells. they can be any particular type of cells however epigenetically modified cells can difficultly be stem cells bc it’s difficult to go from specialized to pluripotent
Where does gene regulation occur?
at many lvld how chr is packaged, TF where the gene is positioned in the genome…
What’s the difference bt TF and epigenetic modifier?
the epigenetic modifier can change the level of transcription for example at a promoter region whereas a TF can only control the rate of transcription.
hist chr DNA ? which order?
DNA+histones = chr
How’s a mutation in normal genetics?
tit affects the germ line so passed through generations
How’s a mutation in epigenetics?
they’re NOT mutations they’re alterations and affect somatic cells (however there’re some examples of epigenetic modifications that persist through generations)
mutations or alterations in epigenetics?
the histone changes or modification of gene expression are alterations NOT mutations
DNA methylation what is it?
It’s the addition of a methyl group to the 5th carbon of e.g cytosine to form methyl citosine if 5mC is deaminated is converted in Thymine
What does CpG means?
those are CG islands when CG changes to TG
Why are CG islands bad?
because they can cause an stop codon e.g CGA to TGA!!!
What are CG islands for?
if they’re methylated the gene is repressed they can be removed actively or passively
What’s methylation for?
condense chr structure reduce DNA binding of proteins regulate gene expression imprinting x inactivation cancer defense against viruses
What are methyltransferases?
enzymes in charge of methylation
Explain the role of Dnmt1.
DNA methyl transferase 1: to maintain methylation avoiding the dilution of methyl groups
Explain the role of Dnmt3:
DNA methyl transferase 3 de novo methylation: it means that’s the 1st one to methylate a piece of DNA.
demethylation of 5mC explain.
5mC has an intermediate state with a OH group so it’s 5 hydroxy methyl cytosine.
Describe the structure of chromatin fibres. (nucleosomes)
nucleosome: 147 bp of DNA wrapped around a octamer of histones; H2A H2B H3 H4
What are remodeler complexes?
They covealentlty modify the histones and remodel the chromatin structure around nucleosomes
What’s genomic imprinting?
functional difference bt parental genomes
In which stages are imprinted genes involved?
They’re involved in embryogenesis
What does methylation have to do with genomic imprinting?
methylation is essential for the maintenance of imprinting
Maternal imprinting
in >16 imprinted loci are regulated by maternal regulation of the DNA in the promoter seq of the repressed gene and the DNA in the promoter seq of the active gene is not methylated
Paternal imprinting
4 imprinted loci are regulated by paternal methylation of DNA sequence in the intergenic regions
What’s chr X inactivation?
basically all females have two copies of all genes bc two chr X so they should deactivate one of them
What’s gene dosage effects?
It’s basically to balance the amount of genes in F AND IN MALES this is done by deactivating one X chr
Give an example of X inactivation.
Calico cats; always female; XX each X carry a color, therefore sometimes the inactive X can have some genes active.
DNA methylation through development.
imprinting methylation maintained in embryo, everything goes down in germ cell development, finally parental methylation rises to reach the imprinting
