Chp 13

Genomic Imprinting

A process that controls whether certain genes are expressed based on which parent they come from.

Methylation

A process involving the addition of a methyl group to cytosine in DNA, primarily responsible for genomic imprinting.

Histone Methyltransferases

Enzymes that add methyl groups to histone proteins.

Demethylation

A chemical reaction that removes a methyl group from a histone protein.

RNA Interference (RNAi)

A natural process that silences genes by degrading messenger RNA (mRNA).

Dicer

An enzyme that cuts long dsRNA molecules into smaller fragments to silence genes.

Five features of epigenetic modification

1. Alter chromatin structure 2. Transmissible during cell division 3. Reversible 4. Associated with gene transcription 5. Do NOT alter DNA sequence.

Cis-acting regulatory sequences

Regulatory sequences that control gene expression on the same chromosome as the genes they regulate.

Trans-acting regulatory proteins

Proteins that can control gene expression on multiple chromosomes.

Pioneer factors

Transcription factors that can bind to condensed chromatin to help regulate gene expression.

DNase I hypersensitivity sites

Regions of the genome that are sensitive to digestion by the enzyme DNase I, typically found in open chromatin.

SWI/SNF complex

Complex that opens chromatin structure by displacing or ejecting nucleosomes.

HP-1

Protein that binds to methylated histones and stimulates heterochromatin formation to silence transcription.

Covered promoters

Promoters associated with genes whose transcription is regulated (not constitutively expressed).

Enhancers

Regulatory elements that may be located tens of thousands of nucleotides away from the genes they regulate.

Acetylation of histones

Increase in acetylation that is typically associated with gene activation and euchromatin formation.