Chapter 12 Part 2 Flashcards
High levels of glucose inhibit _______, which inhibits the conversion of ATP to cAMP
adenylate cyclase
cAMP binds to _______, which binds to the lac promotor and enhances transcription
Catabolic repressor protein (CRP) or CAP
CAP-cAMP binding physically distorts the DNA allowing for the _______ of the lac promotor to be more accessible to RNA polymerase
major grooves
the ________ mutation is a mutation in the operator where the repressor protein cannot bind to operator
Oc
certain mutations of the lac operon lead to _______ in which the genes are transcribed constitutively whether or not lactose is available
constitutive mutants
What are two important mutations in the lacI gene?
1) I-: repressor mutation where repressor cant bind to operator
2) Is: repressor mutation where repressor cant bind to allolactose
Lac operator mutations are exclusively ________; they influence transcription of genes only on the same chromosome
cis-acting
The lacI gene mutations produce a regulatory protein that is _______; is capable of diffusing and interacting with both operators in a partial diploid
trans-acting
the tetrameric repressor protein binds to the _______ and _______, which induces a DNA loop and blocks access by RNA polymerase
O1 and O2
_______ mutations disrupt the two-fold symmetry of the O1 segment
Oc
The Tryptophan operon is _______ and _______
1) repressible
2) attenuated
Certain repressible operons have second regulatory capability called _______, which can fine-tune transcription to match the immediate needs of the cell
attenuation
Operons involved in anabolic pathways operate through activity of the end product to block transcription of the operon = _______
feedback inhibition
the trp operon contains five structureal genes and a regulatory region with a promoter, operator, and _______ region
leader region (trpL)
outside the trp operon, there is the _______ protein, a repressor protein that is activated when bound to trp
trpR
tryptophan acts as a ______ by binding to the trp repressor and activating it
co-repressor
the trpL region contains 4 repeat DNA sequences and the mRNA produced contains complementary repeats as well as _______ and _______ codons for 14 amino acid polypeptide
start and stop
the trpL sequence contains 2 _______ codons back to back on the 1st repeat sequence of the mRNA
trp
if repeat sequences 2 and 3 pair together, what happens?
forms anti-termination loop
- ribosome does not have any trp to pull from so it stalls on trp codons allowing for regions 2 and 3 to pair
if repeat sequences 3 and 4 pair together, what happens?
forms termination loop
- ribosome has plenty of trp for anticodons and movse over the trp codons and blocks regions 1 and 2
