ch 16 learnsmart

Monod, Jacob, and Pardee learned about the lac operon using bacterial strains called merozygotes. Since lacI encodes a diffusible protein, in a merozygote, the gene on the _____ _____ could supply the mutant cell with functional repressor protein.

F' factor

What is the name for a strain of bacteria containing an F' factor?

Merozygote

Enzyme adaptation refers to the observation that

a particular enzyme appears within a cell only after the cell has been exposed to the substrate for that enzyme.

The observation that a particular enzyme appears within a cell only after a cell has been exposed to the enzyme's substrate is called enzyme

adaptation.

A conformational change that prevents the repressor from binding to the lac operator occurs when _____ binds to the lac repressor.

allolactose

In the thi operon in B. subtilis, when levels of TPP are low, the 5' end of the mRNA forms a stem-loop structure called a(n) _____ that allows transcription to continue.

antiterminator

During attenuation, transcription begins,

but it is terminated before the entire mRNA is made.

Inducible operons usually encode _____ enzymes, and repressible operons usually encode _____ enzymes.

catabolic; anabolic

In the thi operon in B. subtilis, when levels of TPP are high, the mRNA folds into a stem-loop structure that

causes attenuation.

The probability that allolactose will bind to the lac repressor depends on the allolactose _____ in the bacterial cell.

concentration

The binding of the lac repressor to the operator shuts down transcription from the lac operon when lactose is

depleted from the environment.

In attenuation, transcription

is stopped prematurely.

When TPP levels are low, the mRNA of the E. coli thiMD operon forms a stem-loop structure that

makes the Shine-Dalgarno sequence available to the ribosome.

When the product of a gene produced in a metabolic pathway inhibits an enzyme that acts early on in the pathway it is called _____ _____.

negative feedback

It has been shown that the lac operon has three_____ sites to which the lac repressor can bind.

operator

In bacteria, the most common way to regulate gene expression is by influencing

the rate of transcription initiation.