Transcription Regulation Flashcards
what is the lac operon?
a group of genes (operon) that are specific to the uptake and metabolism of lactose and turn it into an energy form of glucose and galactose
how is the transcription of the lac operon regulated by the availability of lactose?
1.) lactose and glucose absent = active repressor and active cap = no transcription
2.) lactose absent but glucose present = active repressor and inactive cap = no transcription
3.) lactose and glucose present = inactive repressor but inactive cap = no transcription
4.) lactose present and glucose absent = inactive repressor and active cap = transcription
basically want lac to be present and gluc to be absent - remember that transcription of lac operon means we make energy form of glucose!
how is cAMP made?
synthesized from atp via adenylate cyclase
what role does cAMP play in the transcription of the lac operon?
acts as a positive regulating signal; when glucose is absent, cAMP will bind a catabolite activator protein (CAP) which will induce transcription
how does glucose prevent lac transcription?
acts as a catabolite repressor when present; cell prefers gluc as an energy source over other forms; + glucose = - cAMP = no lac trans
what are enhancers and what do they do?
sequences that interact with polymerase and allow more efficient transcription; allow multiple transcription factors to bind
what are negative regulatory forces?
regulatory force that can pause transcription soon after initiation begins to help maintain cellular homeostasis; NELF and DSIF are factors
what are positive regulatory forces?
regulatory force that can re-initiate transcription and increase expression
how does chromatin condensation suppress transcription?
condensed chromatin reduces the ability for cis-acting regulatory proteins to bind to trans-acting ones; chromatin needs to be “loose” in order to be transcribed
define chromatin
complex of dna and proteins that assists in packaging long dna into more compact forms
define nucleosome
a segment of dna wrapped around 8 histone proteins; basic structural units of dna packaging
define histones
simple alkaline proteins; act as ‘spools’ for dna to wind around
what is the effect of histone acetylation on transcription?
acetylation will cause the chromatin to decondense which will in turn increase the rate of transcription
how do chromatin remodeling factors work?
remodeling factors can exchange, modify, or remove histones in order to allow access to condensed dna
what effect does dna methylation have on transcription?
a type of epigenetic modification that causes transcriptional repression; addition of cytosine before a guanine will allow for methylation - activity of dna changed but not sequence
