Regulation of Gene Expression I: Prokaryotic Paradigms

what is the basic unit of heredity passed from parent to child?

gene

what is gene expression?

process by which genetic info saved in genes is expressed in RNA and/or protein to support a phenotypes

what is the structure and function of life

gene expression

how is gene expression regulated?

spatially and temporally

what is an operon

a group of genes that are transcribed together and code for functionally similar proteins

what 3 things make up an operon

promoter+ operator+ structural genes

what is the on/off switch in an operon?

operator

where in an operon does RNA polymerase bind?

promoter

relative to the regulatory gene, is the operon on the 5' or 3' end of genes?

3'

reverse transcriptase produces

cDNA (copy or complementary DNA)

what do regulatory genes produce

the repressor (activator) protein

what part of the operon codes for proteins?

structural genes

the terminator is a short sequence at the __' end of the gene to terminate transcription

3'

how many terminators are there per operon?

one

what is a cistron?

genes that are monocistronic or polysistronic

the operator is an example of a ___ regulatory element

cis

regulatory gene is an example of a ___ regulatory element

trans

what is a regulon?

a collection of two or more operons subjected to the same type of coordinated regulation

what does an operon contain?

one or more cistrons, promoter(s), operators and a single terminator

during positive regulation, what is necessary for transcription to occur?

an activator bound to the operator

during negative regulation, what is necessary for transcription to occur?

a repressor not being on the operator

what are the two types of activator operons?

1. positive inducible operon

2. positive repressible operon

what are the two types of repressor operons?

1. negative inducible operon

2. negative repressible operon

the Laz operon is what type of operon?

both positive inducible and negative inducible

The Trp operon is what type of operon?

negative repressible operon

what is necessary for transcription with a Laz Operon- Activator (CAP)?

an activator protein bound to the binding site

what happens when the active repressor binds to the operator in the Laz operon- repressor?

no transcription

what is the activator for the laz-operon activator?

catabolite activator protein

co activator: cAMP

what is the inducer of the laz operon-repressor?

Allolactose, IPTG

the Lac operon is inducible, so it turns on when

lactose is not necessary for the cell to function

when lactose is absent, the repressor is ___ and the operon is ___

lactose absent

repressor active

operon off

when lactose is present, the repressor is ___ and the operon is ___

lactose present

repressor inactive

operon on

what happens to the Laz operon when the environment is as follows:

+ Glucose

+ Lactose

operon is off, CAP is not bound

what happens to the Laz operon when the environment is as follows:

+ Glucose

- Lactose

operon is off, CAP is not bound, the LAC repressor is bound

what happens to the Laz operon when the environment is as follows:

- Glucose

- Lactose

the operon is off, the Lac repressor is bound

what happens to the Laz operon when the environment is as follows:

- Glucose

+ Lactose

operon is on and RNA is being made

when does the CAP bind to the CAP binding site of the Laz operon?

when glucose is not present

when does the repressor bind to the operator of the Laz operon?

when lactose is not present

what happens when tyrptophan is present?

the repressor is active and the operon is off

what happens when tryptophan is absent?

the repressor is inactive and the operon is on

what are 4 different types of gene regulatory cofactors

inducer

inhibitor

coactivator

corepressor

what cofactors regulate repressors?

inducer

co-repressor

what cofactors regulate activators?

inhibitor

co-activator

repressors are a cis/trans regulatory element

trans

what is the function of repressors

they prevent gene expression at the transcriptional level by interacting with RNA polymerase

inducers are small molecular that can

bind to regulator proteins and alter their binding affinity to DNA

what happens when an inducer binds to a repressor?

the repressor becomes unable to bind to its operator and the operon can be transcribed by RNA polymerase

when allolactose binds to an inactivates the lac repressor- what can it be called?

an inducer

what are co-repressors?

small molecules that bind to repressors allowing repressors to bind to the operator and prevent transcription

co-repressors participate in what type of regulation of operon?

negative repressible

function of activators

bind operator and enhance/activate transcription of an operon by RNA polymerase

EX. catabolite activator protein

cyclic-AMP is an example of a

co-activator

inhibitors are small molecules that

bind and prevent activators from binding DNA

inhibitors work in what type of operons

positive repressible operons

what is transcription-translation coupling?

mechanism of gene expression regulation

transcription is affected by its concurrent decoding via translation

(in prokaryotes)

types of transcriptional translation coupling regulation

attenuator control regulation

riboswitch

what is attenuator control regulation in transcription-translation coupling?

involves alternate secondary structures in mRNA

depends upon avaialblility of tRNA charged w tryptophan

what are riboswitches?

structured mRNA elements that regulate gene expression in response to metabolite or second messenger bindings

Ex. lots of guianine --> binds to riboswitch --> change in conformation --> new structure terminates transcription

what are the mechanisms of gene regualtion in prokaryotes

1. transcription translation coupling

2. translation machinery inhibits in multiple cistron coupling

3. translational coupling involves ribosome bindings

Promoter interacts with____ for transcription initiation

RNA polymerase

____ are dominate in prokaryotes.

Repressor

Transcription of cistron produces

RNA or mRNA(s) and then relevant polypeptide(s)

38% operons are ___citronic ones

polycistronic