gene regulation Flashcards
Operon
cluster of related genes with on/off switch
3 parts of operon
promoter
operator
genes
promoter
where RNA polymerase attaches
operator
“on/off”, controls access of RNA poly
genes
code for related enzymes in a pathway
Regulatory gene produces
repressor protein that binds to operator to block RNA poly
repressible operon
on
Anabolic
Organic molecule product acts as corepressor
operon is turned off
inductible operon
off
catabolic
Repressor is active 🡪 inducer binds to and inactivates repressor
operon is turned on
Anabolic
build organic molecules
corepressor
binds to repressor to activate it
catabolic
breaks down food for energy
Positive Gene Regulation
Some operons are also subject to positive control through a stimulatory protein, such as catabolite activator protein (CAP), an activator of transcription
When glucose (a preferred food source of E. coli) is scarce, CAP is activated by binding with cyclic AMP (cAMP)
Activated CAP attaches to the promoter of the lac operon and increases the affinity of RNA polymerase, thus accelerating transcription
When glucose levels increase, CAP detaches from the lac operon, and transcription returns to a normal rate
CAP helps regulate other operons that encode enzymes used in catabolic pathways
what % of genes are expressed at any time in humans?
20
what causes differences between cell types
differential gene expression
Different cell types (with identical genomes) do what
turn on different genes to carry out specific functions
Chromatin Structure allows what
Tightly bound DNA less accessible for transcription
DNA methylation
methyl groups added to DNA; tightly packed; decreases transcription
Histone acetylation
acetyl groups added to histones; loosened; increases transcription
Epigenetic Inheritance
Modifications on chromatin can be passed on to future generations
Unlike DNA mutations, these changes to chromatin can be reversed (de-methylation of DNA)
Explains differences between identical twins
Transcription Initiation
Control elements” bind to transcription factors
transcription initiation enhances
gene expression
Transcription Initiation Complex
Enhancer regions bound to promoter region by activators
proteins processing includes
folding
cleaving
adding sugar groups
targeting for transport
proteins degredation
ubiquitin tagging
proteasome degredation
regulation of mRNA
micro RNAs (miRNAs) and small interfering RNAs (siRNAs) can bind to mRNA and degrade it or block translation
