unit 6 regulation of gene expression
operon
a group of genes that operate together and have related function
what is regulation of gene expression in prokaryotes?
- clusters of genes (operon) regulated - cytoplasm - no histones - no introns - regulation only at the transcriptional level
what is regulation of gene expression in eukaryotes?
- individual genes regulated - nucleus and cytoplasm - DNA is wrapped around histones - introns are present - regulation at all levels
operator of operon
on/off switch
repressors
prevent RNA polymerase from binding to the DNA< preventing transcription
repressible operon
an operon under negative control. It is usually "on" but can be turned "off". - anabolic reaction
inducible operon
an operon under positive control. It is usually "off" but can be turned "on". - catabolic reaction
alternative splicing
different mRNA molecules are reproduced from the same primary transcript depending on which exons are used
what is post-transcriptional regulation?
??
what is regulating chromatin structure?
??
what is regulating transcription initiation?
??
what is regulation of gene expression?
Includes a wide variety range of mechanisms that are used by cells to increase or decrease the production of a specific gene products (protein or RNA) and is formally termed gene regulation
histone acetylation
acetyl groups are added to histones which presents them from binding to DNA as tightly, making room for proteins to bind for transcription
genes of operon
code for proteins
activators
help RNA polymerase bind to the DNA< increasing transcription
initiation of translation
if the ribosome does not form or mRNA cannot attach, translation does not occur
protein processing and degradation
many proteins need to be modified to become active, may be modified by the addition of ubiquitin, which triggers proteasomes to break down the protein
DNA methylation
methyl groups can attach to DNA bases, preventing transcription
mRNA degradation
nuclease enzymes break down mRNA, lifespan of mRNA varies
what are the parts of the operon?
promoter, operator, genes
promoter of operon
where RNA polymerase attaches
