CH 16

Genetics

Cis acting

regulatory region on same DNA strand, acts on same DNA strand

Trans acting

regulatory region is on different DNA strand Homologous strand?

Eukaryotes default activity

off, stimulation regulation

Prokaryote default activity

on, repression regulation

Constitutive enzymes

continuously produced regardless of environment

Lactose

stimulates transcription of lac operon

Allosteric repressor

undergoes conformational changes

Jacob and Monod

operon model of negative control, proposed lac I produces allosteric repressor molecule

I-

repressor can not bind to operator

Oc

operator will not bind with normal repressor

Is mutant

operon is superrepressed because inducer can not bind to repressor

I+

does not relieve repression

Be able to reason through mutants in repressor operator system and in merozygotes

CAP

positive control of lac operon, binds to CAP-binding site facilitating RNA polymerase to bind at promoter

cAMP dependence

in absence of glucose cAMP levels rise forming cAMP-CAP complex which binds to promoter

cAMP inhibition

glucose inhibits adenylyl cyclase which converts ATP to cAMP

Attenuation

leader sequence ahead of structural genes that forms hair pins, contains to trp codons

antiterminator hair pin

in absence of trp, charged tRNA not present causing ribosome to stall and form hairpin

terminator hairpin: in presence of trp, charged tRNAs are abundant ribosome moves past leader and causes termination hairpin

Riboswitches

alternative form of mRNA, binds with small ligands which induce second RNA domain, creating terminator structure

Aptamer

binds to ligand

Expression platform

capable of forming terminator structure

Bacterial small noncoding RNAs

can be negative and positive regulators