Chapter 14 review questions

Define operator

A DNA sequence where a transcription factor (such as an activator or a repressor) bind to change the rate of transcription in prokaryotic cells.

Define regulator gene

A gene that codes for a transcription factor (a protein that regulates transcription, such as an activator or repressor)

In E. coli, the lac operon is under negative control. What does this mean?

A repressor is involved in regulating transcription

Regulatory proteins, also called transcription factors, that bind to DNA and increase the rate of transcription are called __________.

Activators

The phenomenon where a single type of pre-mRNA from a sigle gene is spliced to produce multiple types of mRNA is called __________. It involves removal of different patterns of introns and keeping different patterns of exons from the pre-mRNA. Ultimately, it allows the same gene to produce more than one protein (e.g.: in different cell types of at different stages of development.)

Alternative splicing

True or false: A muscle cell, a neuron, and a skin cell all have the same proteome (i.e.: they produce the same proteins) but have different genomes (i.e.: they have different genes.) This is due to gene regulation - different genes are active in different cell types.

False. It should read: A muscle cell, a neuron, and a skin cell all have the same genome (i.e.: they have the same genes) but have different proteomes (i.e.: they produce different proteins.) This is due to gene regulation - different genes are active in different cell types.

Define structural gene

Gene that codes for proteins

The trp operon is regulated by a repressor, so it is an example of ________ control.

Negative

In E. coli, the lac operon is inducible. What does this mean?

Normally the repressor is active, so transcription is inactive. You can turn on (induce) transcription by turning off the repressor.

Activators and repressors are involved in gene regulation in both prokaryotes and eukaryotes. However, the DNA sequences that they bind to have different names. I prokaryotes, both types of transcription factors bind to DNA at sequences called _________.

Operators

In eukaryotes, transcription factors that decrease the rate of transcription bind to DNA sequences called _________

Silencers (repressors)

For the lac operon in E. coli, suppose a mutation occured in the operator that the repressor would normally bind to, preventing the repressor from binding. Assume no other mutation occurs. What would be the expected effect of this mutation?

The operon would be on except when the glucose levels are high (The amount of lactose would not affect the rate of transcription)

The lac operon in E. coli produces enzymes needed for the bacteria to use the sugar, lactose. The regulation of the operon is affected by the levels of glucose and lactose available in bacteria. Which statement best describes the normal functioning of this operon?

The operon would only be on when lactose levels are high and glucose levels are low.

Define promoter

The promoter is a DNA sequence located at the beginning of the operon/gene that RNA polymerase binds to to being transcription.

In E. coli, the lac operon is under positive control What does this mean?

This means that the activator is involved in regulating the transcription of this operon.

True or false: Gene regulation also allows organisms to produce different proteins at different stages of development. For example, human embryos and fetuses produce different globulin subunits than those produced by adults, so the oxygen affinity of hemoglobin changes during development in humans

True

In E. coli, the trp operon is regulated by a repressor that is normally inactive. The presence of amino acid tryptophan turns on the repressor. a. What effect does this have on transcription? b. Is the trp operon under positive or negative control? Explain. c. Is the trp operon inducible of repressible? Explain.

a. Turning on the repressor slows down or stops transcription b. Negative control, because it is being operated by a repressor c. Repressible (if repressor is normally of and is switched on, it is repressible)

In eukaryotes, transcription factors that increase the rate of transcription bind to DNA sequences called _________

enhancers (activators)

The trp operon is considered a __________ operon because the structural genes needed to synthesize tryptophan are not expressed when the level of tryptophan in the cell is high.

Repressible

Regulatory proteins, also called transcription factors, that bind to DNA and reduce the rate of transcription are called __________.

Repressors

Most gene regulation in bacteria occurs at this level:

Transcriptional control

The rate or occurrence of transcription is regulated

Transcriptional control

Which of the levels of gene regulation is most important in bacteria? Which does not occur at all? Why not?

Transcriptional control is where most gene regulation occurs in bacteria. No post-transcriptional control occurs in bacteria because messenger RNAs are not processed in prokaryotic cells.

Gene regulation in eukaryotic cells occurs at what levels? (4)

Transcriptional control, post-transcriptional control, translational control, post-translational control

Genes that are expressed at all time at relatively constant levels are called ____________ genes

constitutive

Gene regulation in bacteria does NOT occur at this level:

post-transcriptional control

The rate or occurrence of RNA processing is regulated

post-transcriptional control

The activity of a protein is regulated

post-translational control

The rate or occurrence of translation is regulated

translational control