BIOL2202 Lecture Notes - Lecture 16: Dna Replication, Nucleosome, Chromatin
Document Summary
Lecture 16 epigenetic modification of gene expression. Chromatin remodelling decondensing: dna needs to be accessible for dna replication, repair, recombination and transcription, chromatin needs to be modified to make dna accessible. Acetylation: histone acetyl transferase (hat) adds acetyl group, histone deacetylase (hdac) removes the acetyl group, h3k9 acetylation the gene is active. Acetylation makes the genes active: histone methyl transferase (hmt) adds methyl group, histone demethylase (hdm) removes methyl group, different levels of methylation can have different effects. Eg: trimethylation makes the genes very inactive: h3k9 methylation the gene is inactive. Methylation of repetitive dna: areas of the chromosome with very repetitive dna are highly methylated and strongly condensed with protein. Heterochromatin chromatin that is highly condensed dna: centromeric and telomeric dna are examples of heterochromatin. Dispersed repeats chromatin dispersed throughout the genome: eg: viruses and transposons, they are inactivated by methylation and become activated when the host is under stress.
