bio chapter 12

Post-translational gene regulation characteristics

- a polypeptide is cleaved by an enzyme making it active - a phosphate group is added to a protein, making it inactive - the rate of degradation of a protein is increased

transcriptional gene regulation characteristics

- an activator binds to an enhancer - a repressor binds to a promoter

Increase in gene expression

- decrease in compaction of histones - acetylation of histone tails - removal of histones from a region

Decrease in gene expression

- increase in compaction of histones - removal of acetyl group from histone tails

Post-transcriptional gene regulation characteristics

- stability of an mRNA is regulated - The correct removal of introns of a pre-mRNA is prevented - export of an mRNA to the cytoplasm is blocked

Translational gene regulation characteristics

- the ability of an mRNA to bind to ribosomes is changed - The 5' end of an mRNA forms a shape that blocks translation

Why is the the ability of glucose to affect transcription of the lac operon an advantage for the bacterial cell?

Glucose is the preferred sugar for the bacteria. If glucose is present, lactose metabolism is suppressed by down-regulating transcription of the lac operon.

What statement about regulation of ferritin is FALSE?

IRP aids in ribosomal binding to ferritin mRNA.

How is it possible for a single gene to encode more than one polypeptide?

Introns can be removed from pre-mRNA in different combinations.

How does the cell recognize that lactose needs to be metabolized?

Lactose is converted into allolactose, which inhibits the lac repressor.

What would probably NOT increase the accessibility of the DNA for gene transcription?

Methylation of DNA

If lacO were mutated, what effect would this have on lactose metabolism?

The repressor would not properly bind to the operator, and the lac operon would be over expressed

How does glucose affect the lac operon?

When glucose levels are low, cAMP levels are high. cAMP binds to and activates the CAP protein, allowing it to bind

A protein that binds to DNA and activates transcription of some genes is a/an ______

activator

Function of ___________ can be modulated by binding of small effector molecules, protein-protein interactions, or covalent modifications

activators and repressors

In the absence of lactose, the lac repressor is

active and can bind to the operator.

The lac repressor is inactivated by binding to which of the following?

allolactose

When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon

cAMP; switches on

DNA is associated with proteins to form

chromatin

The idea that gene regulation involves multiple factors is called ________

combinatorial control

Removal of acetyl groups from histones results in a/an ________ in gene expression

decrease

Valid reasons for a cell to regulate gene expression include its ability to keep a gene product available under all conditions

false

Valid reasons for a cell to regulate gene expression include its ability to synthesize mRNA for every gene in the genome at all times

false

The lac operon is expressed when

glucose is low and lactose is present.

An activator can increase transcription by attracting a ____________ to the region

histone acetyltransferase

Addition of (-COCH₃) groups to histone amino terminal tails results in a/an ______ in gene expression

increase

When a transcription factor interacts with DNA

it forms noncovalent bonds with functional groups on the nitrogenous bases.

The lac repressor binds to what site within the lac operon?

lacO

Which region associated with the lac operon is NOT involved in the binding of RNA polymerase to the DNA?

lacZ

Which of the following is not part of the lac operon?

lacl

Modification of bases in DNA, usually resulting in inhibition of transcription, results from ________

methylation

A _______ is composed of DNA wrapped around an octamer of histone proteins

nucleosome

RNA polymerase binds to the

promotor

At which of the following level(s) can gene expression be regulated in eukaryotes?

rate of protein synthesis initiation of transcription passage of mRNA through the nuclear membrane destruction of the mRNA

A protein that binds to DNA and blocks activation of a small number of genes is a/an _______

repressor

How does the cell regulate the initiation of transcription in eukaryotes but not prokaryotes?

through basal transcription factors

The most efficient control of eukaryotic gene expression is achieved at the level of

transcription initiation

What level of regulation do eukaryotes possess that prokaryotes do not?

transport of RNA out of the nucleus

Valid reasons for a cell to regulate gene expression include its ability to execute a specific program of development (e.g. to become a blood cell or immune cell)

true

Valid reasons for a cell to regulate gene expression include its ability to make additional cells of the same type in response to a demand

true

Valid reasons for a cell to regulate gene expression include its ability to stop synthesis of a cellular component when there is enough available in the cell.

true

Valid reasons for a cell to regulate gene expression include its ability to synthesize enzymes to metabolize a particular nutrient

true