chapter 18 quiz

Muscle cells differ from nerve cells mainly because they

express different genes.

A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in

continuous transcription of the structural gene controlled by that regulator.

Within a cell, the amount of protein made using a given mRNA molecule depends partly on

) the rate at which the mRNA is degraded.

Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?

Allolactose binds to the repressor protein.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase gene and the permease gene, which of the following would be likely?

Beta galactosidase will be produced.

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?

Continuous transcription of the operon's genes

Which of the following statements about the DNA in one of your brain cells is true?

It is the same as the DNA in one of your heart cells.

In eukaryotes, general transcription factors

bind to other proteins or to a sequence element within the promoter called the TATA box.

The role of a metabolite that controls a repressible operon is to

bind to the repressor protein and activate it

A lack of which molecule would result in the cell's inability to "turn off" genes?

corepressor

The fact that plants can be cloned from somatic cells demonstrates that

differentiated cells retain all the genes of the zygote.

Genomic imprinting, DNA methylation, and histone acetylation are all examples of

epigenetic phenomena.

If you were to observe the activity of methylated DNA, you would expect it to

have turned off or slowed down the process of transcription.

Mutations in which of the following genes lead to transformations in the identity of entire body parts?

homeotic genes

Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation?

inducer

Which of the following, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator?

inducer

When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?

methylation and phosphorylation of histone tails

Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene

normally leads to formation of head structures.

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?

proto-oncogenes normally help regulate cell division

Which of the following is a protein produced by a regulatory gene?

repressor

If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then

the amino acid acts as a corepressor.

The lactose operon is likely to be transcribed when

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

Cell differentiation always involves

the production of tissue-specific proteins, such as muscle actin.

Which of the following is an example of post-transcriptional control of gene expression?

the removal of introns and alternative splicing of exons

The functioning of enhancers is an example of

transcriptional control of gene regulation

The tryptophan operon is a repressible operon that is

turned off whenever tryptophan is added to the growth medium