DAT: 9.14 Epigenetics

Epigenetics

• heritable changes in gene expression

• NO DNA sequence change

• reversible

• lower gene expression

• Transcription factor binding is inhibited

• Attract proteins to bind tightly to histones

• added to genome @ Deoxyribose sugar of the DNA strand

DNA methylation

• more gene expression

• Acetyl groups are added to lysine residues of histone tails

• electrostatic affinity between DNA and histone proteins decreases

• associated w/ euchromatin

Histone acetylation

RNA Interference

• silencing gene by destroying/blocking its mRNA

• NO mRNA→ NO protein

siRNA

slice mRNA

miRNA

mute translation

Agouti Mouse Experiment

• methyl-rich diet→ normal & brown

• NO methylation→yellow & obese

Temp Dependent Sex Determination

sex depends on temp

• cold temp→male

• warm temp→female

Pattern I (Turtles)

• medium temp→male

• cold or hot temp→female

Pattern II (Crocodiles)

Honeybee

• royal jelly→queen

• normal diet→worker

Gene upregulation

DNA demethylation

• Genomic imprinting

• Failure to express paternal genes

Prader-Willi Syndrome

• Alteration in gene expression depending on which parent the allele is inherited from

• imprinted allele is silenced

Genomic Imprinting

occurs during mitotic division of embryonic cells

X-inactivation

Loss of gene expression on the maternal chromosome

Angelman syndrome

• Gene expression regulation 

• binds to Complementary coding RNA 

non-coding RNA

inhibition of translation by non-coding RNA

RNA interference

• Prevents DNA methylation which produces the queen phenotype 

• development of a queen bee

royal jelly