T1Q5: Epigenetics Flashcards
• distinguish between epigenetic and genetic inheritance • distinguish functional and structural differences between 2 heterochromatin types and euchromatin • understand how gene expression states can determine phenotype • understand basic mechanisms and examples of epigenetic gene regulation • understand overall principle of how imprinting works and how it can lead to atypical inheritance patterns
chromatin
euchromatin: loose chromatin
heterochromatin: dense chromatin
condensation
nucleosomes
30 nm flaments
solenoid
macrostructure
heterochromatin
condensed chromatin
constitutive heterochromatin
def. regions of chromatin that are always highly condensed
ex. telomeres, centromeres
euchromatin
def. regions of chromatin that are less condensed
ex. expressed genes
facultative heterochromatin
def. euchromatic regions that can assume a more condensed state
ex. X chromosom, paretnally imprinted genes, genes expressed in developmental stages
DNA methylation
transcriptional repression and reduced or absent gene expression
DNMT3a, DNMT3b
def: de Novo Methyltransferases
function: methylate cytosines of DNA (inactivate)
histone acetylation
REPRESSION
addition of acetyl groups to lysine residues in H2A, H2B, H3, and H4
histone methylation
BOTH
addition of methyl groups to arginine residues
histone code
refers to overall patter of all histone modificaitons and the effect of this pattern on gene expression and potential for gene expression
HAT
def: histone acetyltransferases
sign: activate gene expression
func: add acyl groups to lysine residues in H2A, H2B, H3, and H4
HMT
def: histone methyltransferases
sign: both gene expression AND expression
func: add methyl groups to arginine residues in H2A, H2B, H3, and H4
chromatin remodeling complex
def:
sign: both repress and activate transcription
func: a catalytic ATP subunit remodels chromatin by changing histone-DNA contacts
Xist
def: a gene on the X-chromosome inactivation center
sign: x inaction
func: produces RNA that coats inactivated X chromosome
