MasteringGenetics Ch15 HW – Flashcards
Unlock all answers in this set
Unlock answersquestion
Which term is used to describe enzymes that are produced only when specific substrates are present in the environment?
answer
inducible
question
What is the role of the lacZ gene product, the enzyme ß-galactosidase?
answer
It converts lactose to glucose and galactose.
question
Which of the following is an example of positive control in operons?
answer
the action of the catabolite activator protein (CAP) in the lac operon
question
Which of the following mutations could lead to constitutive expression of the genes of the lac operon?
answer
A mutation in the operator sequence
question
Which of the following best describes the biological role of the lac operon?
answer
It ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment.
question
The placement of the operator sequence between the promotor and the structural genes is critical to the proper function of the lac operon.
answer
true
question
Which of the following statements best describes the trp operon?
answer
It is repressible and under negative control.
question
The enzymes involved in lactose metabolism are
answer
needed when lactose is present.
question
The enzymes involved in tryptophan metabolism are
answer
needed when tryptophan is absent.
question
In positive control of gene expression,
answer
the regulatory molecule stimulates transcription.
question
In negative control of gene expression,
answer
removal of the regulatory molecule from DNA stimulates transcription.
question
Line (a)
answer
The repressor is bound to the operator, and CAP is bound to its binding site. The operon is not transcribed.
question
Line (b)
answer
The repressor is inactive, and CAP is bound to its binding site. The operon is being transcribed at a high level.
question
Line (c)
answer
The repressor is bound to the operator, and CAP is not bound to its binding site. The operon is not transcribed.
question
Line (d)
answer
The repressor is inactive, and CAP is not bound to its binding site. The operon is transcribed at a low level.
question
Under a system of positive control, transcription does not occur unless a regulator molecule directly stimulates RNA production.
answer
true
question
The enzyme permease cleaves the linkage between glucose and galactose residues in lactose.
answer
false
question
The lac operon consists of three structural genes as well as the adjacent region of DNA known as the regulator.
answer
false
question
Which term most appropriately refers to a regulatory protein in prokaryotes?
answer
DNA binding protein
question
Which of the following occurs as a result of an abundance of tryptophan in E. coli?
answer
The 5 trp genes (TrpA - TrpE) are not transcribed.
question
Which of the following features of the trp operon is likely least essential to the process of attenuation?
answer
The order of the structural genes, E, D, C, B, A
question
Attenuator systems such as the one described for regulation of tryptophan synthesis would be just as likely to occur in eukaryotes as in prokaryotes.
answer
false
question
The trp and lac operons are both subject to forms of control that are typically called negative.
answer
true
question
When referring to attenuation in regulation of the trp operon, it would be safe to say that when there are high levels of tryptophan available to the organism, ________.
answer
transcriptional termination is likely
