'branch of bio which studies the casual interactions between genes and their products, which bring the
phenotype into being'
epigenetics - changes in gene expression that do not change the DNA sequence
epigenetic mechanisms - * DNA methylation and histone modifications
other: epitransctiptome, regulatory RNA
epitranscriptome - collection of all the chemical modifications in RNA in a cell
discovery of chromatin - -1882- 'chromatin' was a term used to describe the darkly stained DNA in the
nucleus
chromocenter - an aggregate of heterochromatin from different chromosomes (DAPI rich when stained)
-found in mice, but not in humans
is chromatin static? - no; chromatin is highly dynamic and can switch between hetero and eu chromatin
dynamic changes in chromatin structure - mediation of gene transcription
regulation of expression by epigenetic mechanisms
occurs during development and t/o life
has high impact on human disease (cancers, etc.)
difference between prok and euk - know this in regards to DNA
linear, circular
, histone, no histones
nucleus, anucleate
how much of the euk genome is active? - not much— most of it is transcriptionally inactive
-theses regions are condensed into higher order chromatin structures
basic level of chromatin organization - involves nucleosome array and 11nm beads on a string fibre
(solenoid formation!)
30 nm fiber - suggested higher level of organizataion
-occurs in vitro, but likely not in vivo as the chromatin is in a higher energy state
nucleosome structure - 147 bp stretch of DNA that is wrapped around a histone octamer (H2A, H2B, H3,
and H4 dimers)
-joined by linker DNA
linker DNA - region between nucleosomes (20-50 bp stretch)
are linker or nucleosomal DNA sequences more accessible for transcription? - linker sequences are more
readily accessible as they do not have histones covering them
how do nucleosomes impact gene transcription? - -negative regulators (nucleosome occupancy/position
is important for gene expression)
nucleosome occupancy - number of nucleosomes associated with a particular region of DNA
high nucleosome occupancy - the gene will be less active as nucleosomes negatively regulate it
aka nucleosome rich regions
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