APBIO 5.6

Operons

regulate gene expression

operator + promoter + genes they control = an operon

operator

segment of DNA that is a regulatory switch for operons and next or in promoter

protein repressor

prevents gene transcription by binding to operator and blocking RNA polymerase

made by a regulatory gene

repressor can turn on and off

repressible operon (trp)

usually on

binds to operator to turn transcription off

function in anabolic pathways

creation of repressible is hindered when there is high levels of an end product

inducible operon (lac)

usually off

contain enzyme gene that code for hydrolysis and metabolism of lactose

in catabolic pathways

enzyme production is regulated by

feedback inhibition or gene regulation

feedback inhibition

gene regulation

regulation in eukaryotes

occurs at any and all points from DNA to final polypeptide

histone acetylation

acetyl groups attach to + charge lysines in histone tail or DNA itself to loosen chromatin structure and allow transcription

methylation

methyl groups attach to histone tail or DNA itself to tighten chromatin structure and impede transcription

RNAi (interference)

miRNA and siRNA can bind to RNA to degrade or block translation

gene expression causes

cell specialization

differential gene expression

cells with the same genome expression genes differently

repressible operon

trp . anabolic pathways. usually on so not active repressor

inducible operon (ex.lac)

lac. catabolic pathways. usually off so active repressor

repressors can be

activated by co-repressor

inactivated by inducer

Eukaryotic regulation occurs…

at any point

euchromatin

chromatin that is looser and usable

alternate RNA splicing

a gene can code for multiple proteins due to altered RNA splicing

microRNAs (miRNA) and interfering RNAs (siRNA)

bind to an RNA strand to degrade it or block translation