33 terms

AT Prokaryotic

prokaryote gene regulation
RNA polymerase
____is the key enzyme for transcription
Initiation , elongation and termination
RNA polymerase is involved in three phases of transcription
sigma subunit + core enzyme, binds to promoter, unwinds DNA, begins polymerization of bases complementary to DNA template
the movement away from promoter sigma subunit released, polymerization
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
Translation in _______ starts before transcription ends.
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__________
stimulation of protein synthesis during lactose utilization
molecule that stimulates synthesis during lactose utilization
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.
Because genes are ___ they are transcribed together as single mRNA
cluster of genes
lacA, lacY and lacZ
genes that split lactose into glucose and galactose
___ 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
Inducers ____ repressor from binding to operator
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
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
mutant repressor cannot bind to operator, operator end of repressor deformed enzyme produced constitutively
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