modules 35, 36, 37 apbio unit 6

prokaryotes

-transcription and translation coupled

-regulates transcription

operons

-organized cluster of genes--> contributing to metabolic task (specific)

-inducible(OFF)(lac operon)

-repressible(ON)(trp operon)

lac Operon

-inducible

-degests lactose

-usually OFF

-negative and positive control

negative-repressor removed by inducer

positive-CAP (cAMP) boosting transcription

when lactose present

-inducer(allolactose) binds to repressor changing its shape so it cant bind to promoter

-RNA polymerase transcribes making genes to digest lactose

when lactose absent

-repressor able to attatch to operator (region of promoter) blocking RNA polymerase from transcribing

trp operon

-repressible

-synthesizes tryptophan

-usually ON

negative-repressor activated by trp and stops transcription

when tryptophan present

-corepressor (tryptophan) binds to repressor protein changing its shape so it can bind to promoter

-RNA cant transcribe genes to create more tryptophan

up regulation

-way to increase rate of transcription of an operon

ex.CAP/cAMP

when lactose is low & glucose is high

-upregulation

-cAMP is high binds to CAP activating it

activated CAP/cAMP complex--> increases rate of transcription

when lactose is present & glucose is present

-cAMP is low, not bound to CAP (inactivated)

-very little lac gene transcription

-prefers glucose over lactose

eukaryotes

-regulates @ every step of protein synthesis

-decoupling allows for more control points

lvls of control

1)DNA Access

2)Pre transcription

3)Post-Transcription

4)Pre-Translation

5)Post-Translation

DNA Access

-only keep neccessary genes accessible

-DNA wound around histoine proteins

-acetyl groups-less tightly packed

-methyl groups-more tightly packed

heterochromatin-more tightly packed

euchromatin-less tightly packed

acetyl groups

usually loosed DNA, less tightly lacked

methyl groups

usually tightens DNA, more tightly packed

heterochromatin

more tightly packed DNA-->unavailable for transcription

euchromatin

less tightly packed-->available for transcription

pre transcription

-"all actors need to be present for the play to begin"

-transcription factors-mediate RNA polymerase

-genes interact with upstream regulatory elements (DNA seq that preceeds transcription seq.)

proximal control elements

enhancer(distal control elements

transcription factors

Collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription.

-pre transcription

-availabilty of it is one major way cell accomplish cells to differentiate to diff funtions(differentiated gene expression)

proximal control elements

Control elements located close to the promoter

Still do the same job of binding proteins to DNA so that transcription can take place

-pre transcription

enhancer (distal control element)

-distant DNA sequence that boosts a gene's activity by helping transcription factors increase gene expression.

-pre transcription

-activators(proteins) bind to it (specific)

-diff cells produce diff activators to create needed genes

post transcription

5'capping&3'poly A tail-->neccessary for mRNA to remain functional and be transported to cytoplasm for translation

alt splicing-->allow for multiple functional gene products to be made from single primary transcript

pre translation

RNA interference

-mediated by miRNA

-any mRNA sequence complementary to miRNA(specific) gets tagged by miRNA either degraded or blocked

-siRNA-->exogenous(lab, virus, made)

miRNA

-endogenous(from inside nucleus)

-any mRNA sequence complementary to miRNA(specific) gets tagged by miRNA either degraded or blocked

degraded-perfectly hybridizes, signal ubiquitin, broken down

blocked-not perfectly hybridizes, translation blocked

post translation

dont let uneccessary proteins hang around

ubiquitin-plentiful in eukaryotic cells

-tag uneccessary proteins for transport to a protasome

inside protasome-->protein broken down, abundant in eukaryotic cells