Epigenetic Inheritance

Heritable modifications to gene expression that don’t involve changes to DNA sequence

DNA methylation: C’s of CpG doublets

Changes in chromatin structure: - Covalent modifications of histones:

Acetylation or Methylation of Lysines - Changes in levels of chromatin compaction

Alters ability of TFs to:Bind to DNAActivate txn

Humans have 23 pairs of chromosomes2 Sex chromosomes (X & Y)22 Autosomes

Dosage Compensation: Female & male cells must express X-linked genes at same levels.

X-inactivation in female mammals

At random, Xist gene from one X is transcribed at higher levels & Xist RNA coats X chromosome in cis.

Heterochromatin:highly condensed chromatin

Calico Cats

Females, heterozygous for alleles of an X-linked coat color gene

Parental ImprintingExpression of alleles of some autosomal genes (rare) is determined by

which parent they’re inherited from.

Prader-Willi Syndrome (PWS)

PWS gene is methylated during oogenesis

PWS gene is not methylated during spermatogenesis

Txn of genes is regulated by binding of TFs to enhancers/silencers.

Chromatin structure can modulate ability of activators to bind to DNA &/or activate txn.