AT Prokaryotic

Created by simingto 

Upgrade to
remove ads

33 terms · prokaryote gene regulation

RNA polymerase

____is the key enzyme for transcription

Initiation , elongation and termination

RNA polymerase is involved in three phases of transcription

Initiation

sigma subunit + core enzyme, binds to promoter, unwinds DNA, begins polymerization of bases complementary to DNA template

Elongation

the movement away from promoter sigma subunit released, polymerization

Termination

the signal reached by RNA polymerase at the end of transcription

Rho dependent Termination

Rho factor recognizes sequence in mRNA, binds to it, and pulls it away from RNA polymerase

Rho independent Termination

stem loop structure formed by sequence of 20 bases with a run of 6 or more U signals release of RNA polymerase

prokaryotes

Translation in _______ starts before transcription ends.

Initiation

for translation signal ribosomes to bind near 5' end of mRNA while downstream transcription is still occuring

Polycistronic mRNA

often leads to the translation of several genes at the same time from one mRNA transcript

regulation of gene expression

1. binding of RNA poly to promoter 2. shift from initiation to elongation 3.release of mRNA at termination 4.posttranscriptional stability of mRNA
5. efficiency of ribosomes to recognize translation initiation sites 6.stability of polypeptide product

lactose utilization

The presence of lactose induces expression of the genes required for__________

Induction

stimulation of protein synthesis during lactose utilization

Inducer

molecule that stimulates synthesis during lactose utilization

Lactose

inducer of genes for lactose utilization

Monod and Jacob

proposed operon theory of gene regulation

Operon Theory

Single signal can simultaneously regulate expression of several genes that are clustered together on a chromosomes and involve the same process.

clustered

Because genes are ___ they are transcribed together as single mRNA

Operons

cluster of genes

lacA, lacY and lacZ

genes that split lactose into glucose and galactose

promoter

___ is the site to which RNA polymerase binds

trans acting elements

can diffuse through cytoplasm and act at target DNA sites on any DNA molecule in cell ( repressor)

cis acting elements

(operator site) can only influence expression of adjacent genes on same DNA molecule

prevent

Inducers ____ repressor from binding to operator

Repression

In absence of lactose, repressor binds to operator which prevents transcription, negative regulatory element

repressor protein

if there is no lactose in cell, a ____is bound to operator Z, Y, and A genes can't be expressed

Lactose present

1. allocation binds to repressor 2. repressor changes shape and cannot bind to operator 3. RNA poly binds to promoter and initiates transcription of polycistronic RNA

Complementation analysis

identified three genes (lacZ, LacY and lacA) in a tightly linked cluster

lac mutants

Monod et al. isolated many __ unable to utilize lactose

lacl+

normal repressor end can bind to operator or normal inducer end, if inducer can bind to repressor, repressor cannot bind lacA, Y and Z are transcribed

lacl-

mutant repressor cannot bind to operator, operator end of repressor deformed enzyme produced constitutively

lacls

superrepressor mutant repressor, inducer can not bind to repressor, repressor can bind to operon even when inducer are present, enzyme are not produced

Mutant operator

nucleotide sequence is changed, repressor cannot bind to operator lac enzymes are synthesized contitutively

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set