Epigenetics Flashcards
What are the mechanisms of chromatin compaction?
DNA methyltransferases mark genes for silencing by placing methyl groups on cytosines
A compartments of chromatin
open, active; includes housekeeping genes, tissue-specific genes, and regulatory elements
B compartment of chromatins
condensed
imprinting
selective silencing of one allele of certain genes
epigenetic phenomenon
change in the phenotype that is heritable but does not involve changes in the order of base sequences of the DNA
Prader-Willi syndrome
paternal deletion of imprinted region on chromosome 15
Angelman syndrome
maternal deletion of imprinted region on chromosome 15
IGF2
enhances growth and cell proliferation
Russel-Silver syndrome
ICR/H19 is not methylated in the paternal allele so H19 will not be suppressed –> two copies of H19 but no IGF2 leads to undergrowth
Beckwith-Wiedemann syndrome
maternal H19/ICR is methylated resulting in no expression of H19 but two copies of IGF2 –> leads to overgrowth
exposure to famine during first trimester
birthweight is normal but adult onset of many diseases (obesity, cardiovascular disease, schizophrenia, depression)
exposure to famine late in gestation
birthweight is low but few adult onset diseases (insulin resistance and hypertension)
Which genes affected by the Hunger Winter?
it is likely that the famine induced dysregulation of methylation of IGF2 (methyl groups were removed to allow expression) which is what caused the later obesity
How are epigenetic changes passed through male lineage?
solenoids may remain in sperm which can preserve methylation/histone-modification marks
plasticity
ability of genotype to produce different phenotypes in response to different environments
