Gene Dosing & Genomic Imprinting Flashcards
what kind of expression majority of genes?
bi-allelic
what mechanisms are involved in X-chromosome inactivation? 3 things
epigenetic mechs
- histone mods
- DNA meth
- non-coding RNAs
mono-allelic expression sufficient?
Many are
Some it’s not like autosomal dominant, aneuploidies
When is mono-allelic expression essential?
many in imprinted genes
The inactive X is called?
Barr body
what starts the X-chromosome inactivation process? then what spreads?
Xist and long non-coding RNA, then leads to heterochromatin spread and DNAmethylation
is the same X inactivated in all cells?
Nope. Most women are mosaic.
How does X-inactivation affect daughter cells?
that first choice of X-chromosome inactivation during an embryo is passed down to daughter cells
when do you get X-chromosome inactivation?
early embryogenesis
are all genes on the inactivated X-chromosomes affected?
nope. some genes escape as they need to be expressed bi-allelically also Turner Syndrome proof that you need the Barr body
4 causes of disruption of imprinting:
- loss of heterozygosity (microdeletions)
- uniparental disomy
- epimutations
- point mutations
Maternally expressed genes tend to do what?
limit fetal growth
Paternally expressed genes tend to do what?
promote fetal growth
Imprints in gametogenesis?
Erased and re-establish and maintained in embryogenesis
what does genomic imprinting mean?
parental origin of a particular gene is ‘marked’ by a reversible epigenetic mechanism