Biology Chapter 19

In humans and other mammals, dosage compensation is achieved by:

females randomly inactivating one X chromosome in each cell.

Gene regulation can occur at which of the following steps in the path from DNA to protein?

during transcription from a chromosome, during translation from DNA to RNA and after protein synthesis

Regulatory transcription factors: (select all correct choices)

bind to DNA sequences in or near enhancer genes. recruit components of the transcriptional complex of proteins.

Epigentic mechanisms of gene regulation ___________ and are ___________.

can be inherited by daughter cells; often reversible and responsive to environmental change

In prokaryotes, inducers are small molecules that:

bind to repressors and promote transcription.

Which of the following questions is about gene regulation? Select all correct choices.

Where are genes for hemoglobin expressed? How much insulin is produced after a meal?

Histone modification

can change over time in response to environmental cues, allowing genes to be turned on or off as needed.

Gene regulation by siRNA is ____________ in eukaryotes and may have evolved originally as a ____________.

widespread; defense against viruses

In RNA editing:

enzymes change the base sequence of the primary transcript and therefore the protein for which it codes.

An operon is:

a region of DNA consisting of the promoter, operator, and coding sequence for structural proteins.

The process by which a single primary RNA transcript is used to make multiple proteins is called:

alternative splicing.

Which of the following changes could cause the production of a shorter-than-normal protein from a gene? (Select all that apply.)

changes in RNA processing changes in RNA editing

For the lactose operon, lactose is a(n):

inducer

For the lactose operon, the CRP-cAMP is a(n):

activator

At the molecular level, the "choice" between lytic and lysogenic pathways is determined by:

the positive and negative regulatory effects of a small number of bacteriophage proteins produced soon after infection.

Chromatin remodeling refers to the process by which:

nucleosomes are repositioned to expose different stretches of DNA to the nuclear environment.

The 5′ UTR and 3′ UTR of mRNA: (select all correct choices)

-may bind with proteins that transport the mRNA to a specific region in the cell for translation. -may bind with proteins that are localized to one place in the cell and that prevent translation.

The CRP-cAMP complex binds the lactose operon when:

glucose levels are low and cAMP levels are high.

Both miRNA and siRNA work in conjunction with:

a protein complex called RISC to bind primary RNA transcripts in the cytoplasm.

A CpG island is: (select all correct choices)

a cluster of alternating C and G bases in a small region near or in the promoter site of a gene

RNA splicing provides an opportunity for regulating gene expression because

a spliceosome in one cell can "see" as an intron what another spliceosome in another cell "sees" as an exon, allowing different proteins to be produced from the same primary transcript.

Positive and negative transcriptional regulation differ in that:

in positive regulation, the binding of a regulatory protein to the DNA is necessary for transcription to occur; in negative regulation, such binding prevents transcription.

The structural genes of the lactose operon are: (select all correct choices)

-turned off by the presence of lactose. -always expressed unless the operon is turned off by a repressor.

De-methylation of CpG islands can cause activation of transcription of nearby genes. Which modification to histone tails is most likely to result from this type of CpG de-methylation? (Select all that apply.)

triple methylation of lysine on the histone tails

Combinatorial control refers to the fact that:

each gene has a unique combination of several different enhancers.

In prokaryotes, gene expression is regulated at the level of: (select all correct choices)

-transcription. -translation.

Small interfering RNA (siRNA) regulates gene expression by:

inhibiting translation by degrading RNA transcripts

The major mechanism of translational regulation is:

the availability of initiation complex proteins in the cytoplasm.

Activator proteins in prokaryotes experience shape changes in the presence or absence of small molecules. As a consequence: (select all correct choices)

-they may activate genes needed only when such a small molecule is present in the cell. -they may activate genes necessary to synthesize a specific small molecule.

The lacZ and lacY genes are transcribed when:

lactose is present and glucose levels are low.

X chromosome inactivation is caused by the accumulation of

non-coding RNA produced by the Xist gene, which coats the X chromosome and induces methylation, histone modification, and other changes associated with preventing transcription.

A typical gene has ____________ enhancer sequence(s); each enhancer sequence has ____________ regulatory transcription factor(s).

several; one

In general, when cytosine bases in CpG islands are methylated:

transcription is repressed.

Dosage compensation refers to the fact that:

X chromosome genes must be regulated differently in males and females because members of one sex have 2 X chromosomes, whereas members of the other have only 1.