ch 18 mastering

Most repressor proteins are allosteric. Which of the following molecules binds with the repressor to alter its conformation and therefore affect its function? transcription factor inducer cAMP promoter

inducer

Enzyme complexes that break down protein are called _____. lipases ubiquitins amylase proteasomes nucleases

proteasomes why:Proteasomes are enzyme complexes that break down proteins

Protein-phosphorylating enzymes' role in the regulation of gene expression involves _____. protein activation translation protein degradation regulating the transport of mRNA to the cytoplasm RNA processing

protein activation

The nuclear membrane's role in the regulation of gene expression involves _____. protein activation translation protein degradation regulating the transport of mRNA to the cytoplasm RNA processing

regulating the transport of mRNA to the cytoplasm

Which of these is NOT a component of the lac operon? lactose-utilization genes only promoter only regulatory gene only operator only promoter and operator

regulatory gene only why:The regulatory gene, while not a part of the operon, plays a role in regulating the expression of the genes of the operon.

Which of the following molecules is a protein produced by a regulatory gene? inducer operon promoter repressor

repressor

_____ bind(s) to DNA enhancer regions. RNA polymerase Promoters Introns Activators Exons

Activators why:Activators are a type of transcription factor that bind to enhancer regions.

Which of the following enzymes converts ATP to cAMP? Adenylyl cyclase b-galactosidase Galactoside permease ATP synthase

Adenylyl cyclase why:Adenylyl cyclase converts ATP to cAMP, which helps CAP bind and facilitates binding of RNA polymerase to the lac promoter.

Which of the following statements best defines the term operon? An operon is a region of DNA that codes for sugar-metabolizing enzymes. An operon is a region of DNA that consists of a single gene regulated by more than one promoter. An operon is a region of DNA that codes for a series of functionally related genes under the control of the same promoter. An operon is a region of RNA that consists of the coding regions of more than one gene.

An operon is a region of DNA that codes for a series of functionally related genes under the control of the same promoter.

The cAMP receptor protein (CRP) is said to be responsible for positive regulation of the lac operon because ________. CRP bound to the CRP-binding site stimulates the transcription of the lac operon CRP prevents binding of the repressor to the operator CRP binds to the CAP-binding site CRP binds cAMP

CRP bound to the CRP-binding site stimulates the transcription of the lac operon

What is allosteric regulation? In allosteric regulation, genes are expressed constitutively. In allosteric regulation, a gene is turned off by a repressor protein. In allosteric regulation, a gene is turned on by an activator protein. In allosteric regulation, a small molecule binds to a large protein and causes it to change its shape and activity.

In allosteric regulation, a small molecule binds to a large protein and causes it to change its shape and activity.

Under which conditions are the lac structural genes expressed most efficiently? No glucose, high lactose High glucose, no lactose No glucose, no lactose High glucose, high lactose

No glucose, high lactose why:When glucose is absent and lactose levels are high, the lac structural genes are expressed the most efficiently. Without glucose, cAMP is produced and CAP can stimulate transcription of the structural genes. In the presence of lactose, the repressor does not bind to the operator and therefore does not block transcription

What molecule binds to promoters in bacteria and transcribes the coding regions of the genes? DNA ligase A nucleotide RNA polymerase DNA polymerase

RNA polymerase why:RNA polymerase is the enzyme that binds to promoters and transcribes the coding regions of genes into RNA.

What is the function of a spliceosome? protein activation translation protein degradation regulating the transport of mRNA to the cytoplasm RNA processing

RNA processing

What happens to the expression of the lacI gene if lactose is not available in the cell? The lacI gene turns on. The lacI gene increases its rate of transcription. There is no change—the lacI gene is constitutively expressed. The lacI gene turns off.

There is no change—the lacI gene is constitutively expressed. The lacI gene is expressed regardless of the presence of lactose. Only the structural genes of the lac operon are affected by the presence or absence of lactose.

What is the function of the lacZ gene? This gene encodes an enzyme, b-galactosidase, which cleaves lactose into glucose and galactose. This gene encodes an enzyme, b-galactosidase, that cleaves lactose into two glucose molecules. This gene encodes an enzyme, galactoside permease, which transports lactose into the cell. This gene encodes the repressor of the lac operon.

This gene encodes an enzyme, b-galactosidase, which cleaves lactose into glucose and galactose. why:The lacZ gene encodes b-galactosidase, a key enzyme in lactose metabolism. When lactose is present in the cell, the cell expresses lacZ and metabolizes lactose.

Why is the lac operon said to be an inducible operon? When allolactose is present, it induces the activation of the lac repressor. When allolactose is present, it induces repression of gene expression. When activated, the lac operon induces repression of gene expression. When activated, the lac operon induces the production of lactose-digesting enzymes. When allolactose is present, it induces the inactivation of the lac repressor.

When allolactose is present, it induces the inactivation of the lac repressor. why:The lac repressor keeps the production of lactose-digesting enzymes turned off. When allolactose is present, the lac repressor is inactivated, allowing the expression of lactose-digesting enzymes.

Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by _____. allowing each gene to be expressed an equal number of times organizing gene expression, so that genes are expressed in a given order allowing an organism to adjust to changes in environmental conditions allowing environmental changes to alter a prokaryote's genome

allowing an organism to adjust to changes in environmental conditions

How does extracellular glucose inhibit transcription of the lac operon? by strengthening the binding of the repressor to the operator by reducing the levels of intracellular cAMP by weakening the binding of the repressor to the operator by inhibiting RNA polymerase from opening the strands of DNA to initiate transcription

by reducing the levels of intracellular cAMP

Which of the following molecules helps to "turn off" genes in a cell? corepressor operon promoter inducer

corepressor

DNA methylation is a mechanism used by eukaryotes to do what? increase the rate of transcriptioncause apoptosis facilitate the binding of DNA to intermediate filaments terminate transcription inactivate genes

inactivate genes DNA methylation, involving the attachment of methyl groups to certain bases, is a mechanism for the long-term inactivation of genes during development.

Regulatory proteins bind to _____. the operator the lactose-utilization genes the regulatory gene RNA polymerase transcription factors

the operator why:Transcription is inhibited when a regulatory protein binds to the lac operon operator.

In the presence of a regulatory protein the lac operon is _____. transcribed not transcribed transcribed at a faster than usual rateis turned on either transcribed or not transcribed

not transcribed why:The regulatory protein of the lac operon is a repressor.

For a repressible operon to be transcribed, which of the following conditions must occur? RNA polymerase and the active repressor must be present. RNA polymerase must bind to the promoter, and the repressor must be inactive. RNA polymerase must not occupy the promoter, and the repressor must be inactive. A corepressor must be present.

RNA polymerase must bind to the promoter, and the repressor must be inactive.

Which of the following conditions is most likely to cause the lactose operon to be transcribed? The cAMP level is high and the lactose level is low. There is glucose but no lactose in the cell. The cyclic AMP and lactose levels are both high within the cell. There is more glucose in the cell than lactose.

The cyclic AMP and lactose levels are both high within the cell.