HMB265H1 Lecture Notes - Lecture 19: Penetrance, Ctcf, Meiosis

• School: UTSG
• Department: Human Biology
• Course: HMB265H1
• Professor: Maria Papaconstantinou

Document Summary

Twins have same genetic background = same phenotype. Heritable modification in gene function not due to changes in the base sequence of dna. Once they get methylated don"t get gene expression. [2] covalent modification to histone tails (acetylation, methylation, ubiq) Dna is not naked in nucleus, have histones and nonhistones that pack dna into complex structures. [3] non-covalent modification of histones = chromatin remodeling of histone variants. When dna packed into compact structure, nothing available. If accessible for rna polymerase or activators get high levels of transcription. Hypercondensation of chromatin results in silencing of transcription. Natural examples of heterochromatin that stay in heterochromatin state for most of life. Stay inactivated for whole descendants of somatic cells until germ line. Occurs on lysine of histone h3 tails. Histone tails = n-terminal parts of histones that spreading out from the nucleosome. Histone tails amenable for modifications in >100 ways.