BIO207 Epigenetics

what is epigenetics?

the study of the phenomena and mechanisms that cause chromosome-associated heritable changes to gene expression that are not dependent on changes in DNA sequence

what are the characteristics of heterochromatin?

• dense staining with a variety of dyes seen as dark bands

• condensed appearance

• show little to no gene expression

• composed of higher-order chromatin structures

• comprised of repetitive DNA rich regions

what are the two types of heterochromatin?

1) constitutive heterochromatin

• regions that always remain heterochromatic

• never get transcribed

• telomere and centromeric regions

2) facultative heterochromatin

• regions that can interconvert between euchromatin and heterochromatin at different stages

• show regulated gene expression

• gene coding regions

what are the 3 major epigenetic mechanisms?

1) chromatin remodeling by a) repositioning of nucleosomes, b) post-transitional modifications of histones at N-terminal tails

2) reversible modification of DNA by the addition or removal of methyl groups

3) regulation of gene expression by noncoding RNA molecules