BS 161 1st Edition Lecture 34 Outline of Last Lecture I Transcription translation Outline of Current Lecture II Gene expression Current Lecture genes within highly packed heterochromatin are usually not expressed genes in euchromatin are expressed histone acetylation acetyl groups are attached to positively charged lysines in histone tails HAT is enzyme that adds DHAC is enzyme that removes the addition of methyl groups methylation can condense chromatin the addition of phosphate groups phosphorylation next to a methylated amino acid can loosen chromatin histone code hypothesis proposes that specific combinations of modifications help determine chromatin configuration and influence transcription DNA methylation the addition of methyl groups to certain bases in DNA is associated with reduced transcription in some species can cause long term inactivation of genes in cellular differentiation genomic imprinting methylation regulates expression of either the maternal or paternal alleles of certain genes at the start of development epigenetic inheritance the inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence chromatin modifying enzymes provide initial control of gene expression by making a region of DNA either more or less able to bind the transcription machinery operons only occur in prokaryotes control elements segments of noncoding DNA that help regulate transcription by binding certain proteins control elements and the proteins they bind are critical to the precise regulation of gene expression in different cell types
View Full Document
Unlocking...