Genetics Exam 4 Review

You identify a CAP mutant protein that is constitutively bound to the CAP site. Under which conditions will the lac operon be transcribed at high levels in cells that contain this mutant protein? Check all that apply.

- Lactose and glucose are both present - Lactose is present, glucose is not

Select the functional roles of heterochromatin. Check all that apply.

- gene silencing - preventing transposition - preventing viral proliferation

Glucocorticoid hormones activate genes that are involved in which of the following processes?

- synthesis of glucose - mobilization of fats - breakdown of proteins

Thymine dimers are repaired by _____.

- the enzyme DNA photolyase - exposure to light - transfer of an electron to the dimer

Regulation of gene expression may occur at which of the following levels?

- transcription - translation - posttranslation

Transcription of the lac operon results in the production of how many different mRNA transcripts?

1

Arrange the following in the proper order in which they occur during glucocorticoid hormone action.1. Binding of hormone to receptor2. Release of HSP90 proteins3. Entry of hormone into the nucleus

1, 2, 3

What stem-loop conformations favor attenuation in the trp operon?

3-4

Which DNA sequence would also work in place of the following bi-directional enhancer? 5' GTTC 3' 3' CAAG 5'

5' GAAC 3' 3' CTTG 5'

Where is the IRE located in the regulation of ferritin translation?

5′ end of mRNA

In the Jacob Monod merozygote experiment, what was indicated by the presence of a yellow color when b-ONPG was added?

Beta-galactosidase was present.

Which of the following is part of the process of X-chromosome inactivation?

Binding of multiple Xist transcripts to Xic on the X chromosome that will be inactivated

Researchers frequently wish to produce proteins in cells in a regulated fashion so that the effects of the protein can be studied under conditions when it is and is not present. Which of the strategies outlined below would be best suited for these types of studies?

Creating a piece of DNA where the gene for the protein of interest is under control of a glucocorticoid response element.

What are some types of the molecular changes that underlie epigenetic gene regulation?

DNA methylation and chromatin remodeling

You are studying a chromosome in a new animal species. The presence of what element would make you most confident that a region is facultative heterochromatin and not constitutive heterochromatin?

H3K27me

Enzymes which acetylate the positively charged lysines within the core histone proteins.

Histone acetyltransferases

The pattern of histone modification acts much like a language or code in specifying alterations in chromatin structure.

Histone code hypothesis

The Avy allele of the Agouti gene involves the insertion of a transposable element upstream from the normal Agouti promoter. The transposable element carries a promoter that causes the overexpression of the Agouti gene. Mice carrying this allele tend to have coat colors that are more yellow than mice that don't have this transposable element. If pregnant female mice are fed a diet that contains chemicals that inhibit DNA methylation, how would you expect that this diet would affect the coat color of offspring carrying the Avy allele?

Their fur would be more yellow because the Agouti gene would tend to be over expressed.

What would most likely be the effect of expressing a mutant regulatory transcription factor that had a dimerization domain but lacked the ability to interact with mediator proteins?

There would be a decrease in the transcription of genes controlled by the normal dimer.

How does UV light and other nonionizing radiation damage DNA molecules?

They create thymine dimers between adjacent thymines in the DNA chain.

If a drug was developed that could inhibit TFIID binding to the core promoter, what would its effect be on transcription?

Transcription that was currently occurring would finish but there would be no new initiation.

In the absence of glucose, and in the presence of lactose, allolactose binds to the repressor, allowing RNA polymerase to carry on transcription.

True

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

allolactose

A sequence of bases that signals the beginning of transcription.

promoter

In a 2008 experiment, researchers fed bee larvae a diet that should produce worker bees, but also injected the larvae with a DNA methyltransferase inhibitor. Most of the larvae became what type of bee?

queen bees

A regulatory protein that binds to the DNA and inhibits transcription.

repressor

CAP affects which operon(s)?

the lac operon

Why is it important to restore displaced histones to the DNA following transcription?

to prevent transcriptional initiation at the wrong location

Riboswitches have been shown to affect regulation of ______.

transcription and translation

Chemical agents can cause mutations by inducing methylation of guanine residues in DNA.

true

Genomic imprinting is a result of

DNA methylation.

You identify a strain of bacteria that has a mutated trp operator that cannot bind the repressor. Under what circumstances will the trp operator be transcribed?

The trp operon will be transcribed when levels of tryptophan in the cell are low.

If the Trp codons in the trpL gene were mutated to encode another amino acid, what would the result be?

The trp operon would never be transcribed.

If the stop codon in the trpL gene were mutated to encode an amino acid (rather than a stop codon), what would the result be?

The trp operon would only be transcribed when tryptophan in the cell was low.

The lac repressor protein is active in the absence of lactose within the cell.

True

The polycistronic mRNA is transcribed from the lac operon when lactose is present in the cell and glucose is not present.

True

Expression of ______ would inhibit X-chromosome inactivation.

Tsix

If an E. coli cell is exposed to glucose, what happens?

cAMP levels are decreased, which does not allow the CAP protein to bind to its regulatory region.

When glucose is present ____________.

cyclic AMP is low, CAP does not bind to the activator binding site, and transcription is turned off

Activator proteins bind to what type of DNA sequence?

enhancers

During interphase, a eukaryotic chromosome is primarily composed of __________.

euchromatin

An individual that has somatic regions that are genotypically different from each other.

genetic mosaic

Which amino acids are acetylated in histones?

lysine

Translational regulatory proteins recognize specific areas of what molecule?

mRNA

If a mutation occurs in the somatic tissue, approximately how many of the gametes will carry the mutation?

none

A sequence of bases that provides a binding site for a repressor protein.

operator

A group of two or more genes under the transcriptional control of a single promoter.

operon

Enzyme which attaches a methyl group to the number 5 position of the cytosine base, forming 5-methylcytosine.

DNA methyltransferase

In apoptosis, a process of programmed cell death, the cell undergoes controlled degradation of cellular components including nuclear DNA. Researchers have noted that if the DNA is isolated from an apoptotic cell, it appears as distinct bands of multiples of approximately 147 bases in length. Why does this occur?

DNA that is wrapped around the histones is not being degraded.

The methylation of DNA that was previously unmethylated.

De novo methylation

When both glucose and lactose are absent, the highest rate of transcription occurs.

False

Hemimethylated DNA is recognized by DNA methyltransferase, which makes it fully methylated.

Maintenance methylation

Proteins which bind methylated sequences.

Methyl-CpG-binding proteins

Which of the following is a mechanism to imprint genes?

Methylation of cytosine

Which of the following is not an example of translational regulation in prokaryotes?

Phosphorylation of an enzyme

If you wanted to create a gene whose protein product would be expressed under elevated iron levels in a cell what element would you use?

Put an IRE at the 5' end of the mRNA

What is the result when the core histones are acetylated via histone acetyltransferase?

The DNA becomes less associated with the core.

A particular gene has a mutation in its NFR that causes it to bind abnormally tightly to histones. What effect would you expect this mutation has on the expression of this gene?

The expression of the gene would be abnormally low or absent.

If HP1 was mutated such that it could still bind H3K9me but could not bind chromatin-modifying enzymes or chromatin-remodeling complexes, what would be the result?

The heterochromatin in the cell would still be compacted but additional changes in heterochromatin structure would not occur.

The inhibitor of differentiation proteins (Id proteins) are transcription factors that lack a DNA binding domain, but they will form heterodimers with specific partners. What is the effect on a dimer if it is formed with an Id protein?

The heterodimer will not bind to the appropriate enhancer regions and therefore will not stimulate transcription.

If a cell has a mutant lacY gene that produces a non-functional product, which of the following statements is true?

The lac operon cannot be induced because lactose cannot enter the cell.

How would the interpretation of the Jacob, Monod, and Pardee experimental results change if lacO was mutated instead of lacI?

The lac operon has constitutive expression and O has a cis-effect

You identify a CAP protein mutant that is unable to bind cAMP. How will this mutant affect transcription of the lac operon?

The lac operon will never be transcribed at a high rate.

A deletion in an operon removes the promoter. How will that affect the transcript that is produced from the operon?

The transcript will not be produced

A transcriptional repressor that controls the transcription of gene A is not normally active unless bound by an effector molecule X. In a certain cell, the domain of the repressor that binds X is mutated so that X can no longer be bound. With all other factors being the same, what effect do you predict on the transcription of gene A if X is added to the cell when it is already transcribing gene A?

The transcription of gene A will not be affected.

A transcriptional repressor that controls the transcription of gene A is not normally active unless bound by an effector molecule X. In a certain cell, the domain of the repressor that binds to the silencer of gene A is mutated so that the repressor-X complex can no longer bind to its recognition site. With all other factors being the same, what effect do you predict on the transcription of gene A if X is increased in the cell and the cell is already expressing gene A?

The transcription of gene A will not be affected.

You repeat the Jacob, Monod, and Pardee experiment. At the end of your experiment all of the tubes are yellow. What mistake did you most likely make?

You added lactose to all of the tubes.

You repeat the Jacob, Monod, and Pardee experiment. At the end of your experiment all of the tubes are colorless. What mistake did you most likely make?

You forgot to add β-ONPG to the tubes.

For enzymes that are controlled by feedback inhibition

a product of the metabolic pathway inhibits the enzyme.

A regulatory protein that increases the rate of transcription.

activator

A mutation in one gene that reverses the effects of a mutation in a different gene is _____.

an intergenic suppressor

Nucleosome-free regions

are found flanking many actively transcribed genes in eukaryotes.

How does a steroid hormone exert its effect upon a cell?

binds to an intracellular receptor to form a complex that then acts as a transcription factor

The lac repressor __________.

binds to the operator and prevents transcription

An epigenetic change involves a permanent change to a DNA sequence.

false

The enzyme methylguanine-DNA methyltransferase adds methyl groups to guanine bases.

false

Enzymes involved in metabolism are most likely regulated via _____.

feedback inhibition

Cells that give rise to the gametes.

germ line cells

Mutation that can be passed onto offspring.

germ-line mutation

Which of the following is not a common post-translational modification that occurs to histones?

glycosylation

For a riboswitch that controls transcription, the binding of a small molecule such as TPP controls whether the RNA ______________.

has an antiterminator or terminator stem-loop

Regions of chromatin that are more compact are called __________; they are usually found __________ in the nucleus.

heterochromatin; at the periphery

Thymine dimers weaken _____.

hydrogen bonds

A small effector molecule that causes transcription to increase.

inducer

Which of the following best describes regulation of the lac operon?

inducible, under negative and positive control

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

lacI

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

lacO

Which gene is responsible for producing the protein that converts lactose to allolactose?

lacZ

Regulatory transcription factors may be regulated by

phosphorylation

All cells of the body excluding the gametes or cells that can give rise to the gametes.

somatic cells

A mutation that cannot be passed onto the offspring.

somatic mutation

Glucocorticoids are ________ hormones secreted by ________ glands.

steroid; endocrine

Combinatorial control of transcription factors refers to the phenomenon that

the combination of many factors determines the expression of any given gene.

Feedback inhibition frequently involves

the inhibition of the first enzyme in the pathway by the final product of the pathway.

The active site of the lac repressor protein is composed of

the protein domain that binds to DNA.

When both glucose and lactose are present ______________.

the transcription rate is very, very low

During embryonic development, cells destined to become muscle cells have other genes that are inhibited by epigenetic changes such as DNA methylation so those genes are not expressed in these cells.

true

Glucocorticoid response elements function as enhancers.

true

The glucocorticoid receptor is active as a dimer.

true

In a particular E. coli strain, a mutation in the thiMD operon results in improper formation of the stem loop secondary structure making it impossible to bind TPP. There are two enzymes encoded by the thiMD operon. How many of the enzymes encoded in the thiMD operon are translated?

two