Chapter 16

Unregulated genes are also called

Constitutive genes

What type of regulator does not need to be adjacent to the gene(s) it is regulating?

Trans-acting factor

When lactose is depleted from the environment, the _______.

the intracellular concentration of allolactose falls

The product of the lacY gene is required for ______.

the transport of lactose into the bacterial cell

Why is a merozygote better at complementing a mutation in a trans-acting factor than in a cis-acting element?

A cis-acting element must be adjacent to the gene it is regulating.

The operon is flanked by a sequence called a(n)_ that signals the beginning of transcription and one termed a(n) _ that signals the end of transcription.

Blank 1: promoter Blank 2: terminator

What effect would a loss-of-function mutation in the lacI gene and a mutation in operator that prevents repressor binding have?

Both result in constitutive expression of the lac operon.

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

True or false: Effector molecules influence gene expression by binding to DNA.

False

True or false: Gene expression is always the same.

False

True or false: On a regulatory protein, an allosteric site is the same as the active site.

False

True or false: The rate of transcription initiation rarely influences overall gene expression.

False

In the 1950s, which three scientists studied mutations in the lac operon of E. coli?

Monod Jacob Pardee

How does an effector molecule influence gene expression?

The effector molecule binds to a regulatory protein and affects its ability to bind DNA.

True or false: The lac repressor does not completely inhibit transcription of the lacZ, lacY, and lacA genes.

True

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

An operon is a group of two or more genes under the transcriptional control of ______.

a single promoter

Would rescue of a mutation using a merozygote better indicate regulation of a gene by a trans-acting factor or a cis-acting element?

a trans-acting factor

A regulatory protein that binds to DNA and increases the rate of transcription is a(n) ______.

activator

When the lac repressor is bound to the operator, RNA polymerase ______ the lacZ, lacY, or lacA genes.

cannot transcribe

The lacY gene encodes lactose_, a membrane protein

permease

Enzyme adaptation results from the synthesis of specific ______ in response to lactose in the environment.

proteins

Constitutive genes encode proteins that the cell needs ______.

all the time

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

merozygote

A protein such as a repressor that inhibits transcription is exerting ____ _ control of transcription.

negative

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

operator

When the lac repressor binds to the lac_ site, RNA polymerase cannot transcribe the lacZ, lacY or lacA genes.

operator

A loss-of-function mutation in a gene encoding a repressor protein has the same effect as a mutation in the ______.

operator site

A group of two or more genes under the transcriptional control of a single promoter is called a(n)

operon

Transcription regulation by an activator protein is considered to be ______ control.

positive

Experiments by Jacob and Monod demonstrated that enzyme adaptation is due to the regulation of genes during

transcription

A polycistronic mRNA contains the sequence(s) for ______.

two or more genes

The three protein-encoding genes in the lac operon are

lacZ,lacY,lacA

Monod and Jacob studied _ metabolism in E. coli.

lactose

Genes that are regulated by corepressors or inhibitors are called

repressible genes

A regulatory protein that binds to DNA and inhibits transcription is called a(n)

repressor

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

allolactose or lactose

A regulatory site on a protein where an effector molecule binds is called a(n) _ site.

allosteric

In the absence of lactose, the lac repressor ______.

allows very small amounts of lac operon enzymes to be made

The lac repressor protein binds to the operator and ______.

blocks transcription

The small effector molecule produced by the enzyme adenylyl cyclase is ______.

cAMP

Many bacterial species use sugars sequentially. This is called ______.

diauxic growth

The sequential use of sugars by a bacterial cell is called

diauxic growth

The normal lacI gene on the F' factor could rescue the lacI- mutants because the product of the lacI gene encodes a ______.

diffusible protein

The phenomenon in which the level of gene expression can vary under different conditions is

gene regulation

In catabolite repression, transcription is influenced by the presence of ______.

glucose

The transport of ______ into a cell causes a(n) _______ in the concentration of cyclic-AMP by inhibiting adenylate cyclase.

glucose; decrease

Monod, Jacob, and Pardee identified rare E. coli mutants that ______.

had abnormal lactose adaptations

An inducer is a small effector molecule that causes the rate of transcription to ______.

increase

Genes that are regulated by inducers are called _ genes.

inducible

The ______ gene encodes a repressor protein.

lacI

Allolactose is a small effector molecule that binds to the lac repressor and ______.

prevents the repressor from binding to DNA

The binding of ______ to the lac repressor promotes a conformational change that prevents the repressor from binding to the lac operator.

allolactose

The intracellular concentration of the inducer _ remains high as long as lactose is available in the environment.

allolactose

The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is

catabolite repression

A DNA segment that must be adjacent to the gene(s) it regulates is a

cis acting element

Which are functions of the enzyme β-galactosidase?

cleaves lactose into glucose and galactose converts lactose into allolactose

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

concentration, amount, or level

In an operon, the ______ signals the beginning of transcription.

promoter

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

rate of transcription initiation

An inducer could bind to a(n) ______ and prevent it from binding to the DNA, or it could bind to a(n) ______ and cause it to bind to the DNA.

repressor, activator

The CAP site and the operator site are ______ that function in gene regulation.

short DNA segments