Epigenetic Inheritance

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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 DNA Activate txn

Humans have 23 pairs of chromosomes 2 Sex chromosomes (X & Y) 22 Autosomes Dosage Compensation: Female & male cells must express X-linked genes at same levels.

highly condensed chromatin 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 Imprinting Expression 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.