Topic 12

central dogna

flow of genetic information; how we make a protein from DNA sequence

transcription

DNA code copied into messenger RNA (mRNA)

translation

RNA code from DNA used to dictate order of amino acids in a protein

house keeping genes

genes expressed in almost every cell type to perform basic functions

regulated genes

expressed only when needed in response to specific signal; code for proteins that aren’t always expressed in every cell

levels of gene expression regulation control

transcriptional control, pre translational control, post translational control

transcriptional control

slowest, saves most energy; best

pre translational control

moderate

post translational control

fastest, uses most energy

gene regulation in prokaryotic cells

primarily controlled at transcriptional level DNA to RNA; uses operons

operons

turns transcription on and off

operon when its on

gene expressed as protein

operon when its off

gene not expressed as a protein

gene regulation in eukaryotic cells

multi level control; regulation happens at many stages of central dogma

regulation in eukaryotic cells DURING

replication and storage of DNA; transcription

regulation in eukaryotic cells AFTER

post transcription, pre translation, post translation

transcriptional unit

genes that are transcribed into mRNA and then translated into proteins; gene regions following regulatory sequence and regulated by whole operon system

group of genes close to one another are usually involved in…

the same function; encoding proteins that work together

regulatory gene

binding site for proteins that promote or inhibit transcription

promoter

regulatory sequence where RNA polymerase binds to start transcription; controls gene expression by initiating an event

operator

regulatory sequence where repressor binds to block transcription and activator binds to initiate transcription; unique to prokaryotic gene regulation

inducers

interact with either activators or repressors to influence gene expression

types of transcription factors

activators and coactivators

activators

promote transcription

coactivators

enhance transcription by bringing activators and transcriptional machinery closer

prokaryotic promoter regions

coupled with an operator

eukaryotic promoter regions

coupled with a TATA box and transcription factors

promoter analogy

key in the ignition

operator analogy

gate in front of your car

regulatory sequence

allows regulatory proteins to bind and affect gene expression; promoters and operators

positive regulation

positive activator increases gene expression; activator leads transcription and no activator leads no transcription

negative regulation

negative repressor decreases gene expression; repressor leads no transcription and no repressor leads transcription

lac operon

negatively regulated by repressor; transcription of lac gene is usually off and protein production not needed unless lactose needs to be broken down

presence of lactose causes..

allolactose to turn on lac gene; inducer which allows transcription

lac 1

lac repressor

lac Z

beta galactosidase; breaks down lactose into glucose, galactose and allolactose

lac Y

permease; protein channel transporting lactose into cell

lac A

transacetylase; exports excess sugar from cell

lac operon works to increase.

membrane permeability

glucose is more…

energy efficient that lactose

positive gene regulation

only transcribe lactose when its the only energy source

high levels of glucose means

lactose doesn’t need to be digested

low levels of glucose means

lactose needs to be digested

transcription of lac operon is __ with high glucose levels

inhibited

transcription of lac operon of __ with low glucose levels

enhanced

allolactose

binds to repressor and turns it off so operator is no longer blocked

cap stands for

catabolite activator protein; lac operon activator

cap is synthesized in its

inactive form; cAMP needed to activate it

needed to make cAMP

ATP and adenylate cyclase

cap regulation

binds to cap site in promoter and enables RNA polymerase to bind efficiently to transcribe

inhibits aden