Genetics - Exam 4

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

1

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

DNA methyltransferase

The enzymes that add the methyl groups are known as ____________.

DNA methyltransferases

Proteins which bind methylated sequences.

Methyl-CpG-binding proteins

An ___________ is a regulatory protein that increases the rate of transcription.

activator

Activator proteins bind to what type of DNA sequence?

enhancers

What are the two functional domains of genetic regulatory proteins?

1. A site where the protein binds to the DNA. 2. The binding site for the effector molecule

Cells that give rise to the gametes.

Germ line cells

Which genes are under the control of the lac promoter?

The lacZ, lacY, and lacA genes are under the control of the lac promoter.

Which of the following is not part of the lac operon? a. lacO b. lacZ c. lacA d. lacl e. lacP

d. lacl

The result of using different H2A, H2B, and H3 histones in octomers is that ____________ regions of the chromosome are created.

functionally different

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

glycosylation

In DNA replication, the methylation pattern is ____________.

heritable

One or more ____________ proteins may inhibit the ability of RNA polymerase to initiate transcription.

repressor

What the factors that commonly contribute to combinatorial control at the level transcription?

1. One or more activator proteins may stimulate the ability of RNA polymerase to initiate transcription. 2. One or more repressor proteins may inhibit the ability of RNA polymerase to initiate transcription. 3. The function of activators and repressors may be modulated in a variety of ways, including the binding of small effector molecules, protein-protein interactions, and covalent modifications. 4. Regulatory proteins may alter the composition or arrangements of nucleosomes in the vicinity of a promoter, thereby affecting transcription. 5. DNA methylation may inhibit transcription, either by preventing the binding of an activator protein or by recruiting proteins that cause the chromatin to become more compact.

List the steps of gene expression in the correct order.

1. Transcription 2. RNA processing 3. Translation 4. Posttranslation modification

What are the steps of the regulation of gene expression in bacteria?

1. Transcription 2. Translation 3. Post translation

What are the three common ways the functions of regulatory transcription factor proteins are controlled?

1. the binding of small effector molecules 2. protein-protein interactions 3. covalent modifications

Protein that stimulates or increases transcription

Activator protein

Which of these are genetic regulatory proteins and which are small effector molecules? activators, repressors, inducers, corepressors, and inhibitors.

Activators and repressors are regulatory proteins. Inducers, corepressors, and inhibitors are small effector molecules.

The ________________ is a DNA sequence recognized by an activator protein called _____________________________________.

CAP site; catabolite activator protein (CAP)

Suppressor mutation in a different gene than was originally mutated. The suppressor mutation results in an enhanced function but not a new function.

Common pathway

The methylation of DNA that was previously unmethylated.

De novo methylation

DNA sequence that can increase transcription

Enhancer

True or False In a frameshift mutation all of the amino acids before the shift are changed.

False

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

False

True or False: Regulatory elements are usually orientation-dependent.

False: orientation-independent

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

Genetic mosaic

Mutations that can be passed onto offspring.

Germ line mutation

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

If a repressor prevents TFIID from binding to the TATA box, why does this inhibit transcription?

If TFIID cannot bind to the TATA box, RNA polymerase will not be recruited to the core promoter, and therefore transcription will not begin.

Mutation that compensates for a mutation, both of which occur within the same gene.

Intragenic

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

Maintenance methylation

Suppressor mutation occurs in a different gene than the one that was originally mutated. Both proteins are part of a multimeric complex and the suppressor mutation compensates for the original mutation

Multimeric protein

Why do operons occur in bacteria?

One biological advantage of an operon is that it allows a bacterium to coordinately regulate a group of genes that are involved with a common functional goal; the expression of the genes occurs as a single unit

Suppressor mutation in a different gene than the original mutation. The second mutation results in a new enzymatic function for the second protein that compensates for the original loss of function.

Redundant function

Trans-acting factor involved in the inhibition of transcription

Repressor protein

Cis-acting factor that can result in the repression of transcription

Silencer

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

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

The DNA becomes less associated with the core.

Under what conditions is lac repressor bound to the lac operon?

The binding of lac repressor to the lac operon occurs when lactose is not present in the environment—when allolactose is not bound to the repressor.

Why is it beneficial to the bacterium to regulate the lac operon with both a repressor protein and an activator protein?

The repressor protein allows the bacterial cell to avoid turning on the operon in the absence of lactose. The activator protein allows the cell to choose between glucose and lactose.

True or False In the absence of glucose, and in the presence of lactose, allolactose combines with the repressor, allowing RNA polymerase to carry on transcription.

True

True or False The addition of a single nucleotide to the DNA sequence causes a frameshift mutation.

True

True or False: Many regulatory elements are orientation-independent, or bidirectional.

True

Define operon

a group of two or more genes that are transcribed from a single promoter.

The histone H2A, H2B, and H3 proteins that have a different sequence are typically incorporated into ____________ of the octomer cores.

a subset

Which of the following combinations would cause transcription to increase? a. a repressor plus an inducer b. a repressor plus a corepressor c. an activator plus an inhibitor d. none of the above would increase transcription.

a. a repressor plus an inducer

Regulatory transcription factors can be _________ that bind to enhancers and _________ transcription, or they can be ______________ that bind to silencers and __________ transcription.

activators; increase; repressors; inhibit

The lac repressor is inactivated by binding to what?

allolactose

The binding of _________ to lac repressor to __________ to the operator site and thereby ___________ transcription.

allolactose; not bind; increases

The binding of ____________ to the lac repressor causes the lac repressor to ____________ the operator site and thereby _____________ transcription.

allolactose; not bind; increases

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.

A bidirectional enhancer has the following sequence: 5'-GTCA-3' 3'-CAGT-5' Which of the following sequences would also be a functional enhancer? a. 5'-ACTG-3' & 3'-TGAC-5' b. 5'-TGAC-3' & 3'-ACTG-5' c. 3'-GTCA-5' & 5'-CAGT-3' d. 3'-TGAC-5' & 5'-ACTG-3'

b. 5'-TGAC-3' 3'-ACTG-5'

The lac repressor.....

binds to the operator and prevents transcription.

When an E. coli cell is exposed to glucose, how does this affect the regulation of the lac operon via CAP?

cAMP does not bind to CAP and transcription is decreased.

What happens if an E. Coli cell is exposed to glucose?

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

A nucleotide deletion in DNA replication ____________.

causes the amino acids downstream from the deletion to be incorrect

The histone cenH3 is found at the ____________ of chromosomes.

centromeres

A _______________ is a small molecule that binds to a repressor protein, thereby causing the protein to bind to the DNA.

corepressor

When glucose is present.....

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

A second spontaneous lesion that may occur in DNA is the deamination of ____________.

cytosine

In eukaryotes, methyl groups are added to the ____________ residues.

cytosine

Which of the following best describes regulation of the lac operon? a. repressible, under negative and positive control b. repressible, under negative control c. inducible, under positive control d. inducible, under negative and positive control

d. inducible, under negative and positive control

A ____________ mutation decreases the chances of survival and reproduction. The extreme example of a deleterious mutation is a ____________ mutation, which results in death to the cell or organism. On the other hand, a ____________ mutation enhances the survival or reproductive success of an organism. Some mutations are called ____________ mutations because they affect the phenotype only under a defined set of conditions.

deleterious; lethal; beneficial; conditional

The most common type of chemical change that occurs naturally is ____________, which involves the removal of an adenine or guanine from the DNA.

depurination

A mutation in the operator sequence may...

disrupt the ability of the gene to be properly regulated.

The residues that precede the ____________ genes are typically not methylated.

housekeeping

The histone MacroH2A is found on the ____________.

inactivated X chromosome

An ____________ is a small effector molecule that causes transcription to increase.

inducer

Some bind to a repressor protein and prevent it from binding to the DNA, whereas others bind to an activator protein and cause it to bind to DNA. In either case, the transcription rate is increased.

inducers

_________________ are genes that are regulated by inducers.

inducible genes

Methylation usually results in the ____________ of transcription.

inhibition

An ____________ binds to an activator protein and prevents it from binding to the DNA.

inhibitor

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

lacO

Which amino acids are acetylated in histones?

lysine

The most common form of methylation is ____________.

maintenance methylation

DNA ____________ may inhibit transcription, either by ____________ the binding of an activator protein or by recruiting proteins that cause the chromatin to become more ____________.

methylation; preventing; compact

Transcriptional regulation by a repressor is termed __________________.

negative control

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

none

The nucleic acid sequence in mRNA is determined by ____________.

nucleotide sequence in DNA

The _____________________ is a sequence of bases that provides a binding site for a repressor protein.

operator site or just operator

Many regulatory elements are ____________.

orientation-independent

Regulation by an activator is considered to be _________________.

positive control

To facilitate transcription, an operon is flanked by a _____________ that signals that beginning of transcription and a _____________ that signals the end of transcription.

promoter; terminator

A repressor is a ______________ that _______________ transcription.

regulatory protein; inhibits

Genes that are regulated by corepressors or inhibitors are termed ________________

repressible genes

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

repressor

Mutations called ____________ are changes in DNA structure that result from natural biological or chemical processes, whereas ____________ are caused by environmental agents.

spontaneous mutations; induced mutations

Regulatory transcription factors can be modulated by

the binding of small effector molecules, protein-protein interactions, and covalent modifications.

Combinatorial control of transcription factors refers to the phenomenon that

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

Combinatorial control refers to the phenomenon that

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

The active site of the lac repressor protein is composed of

the protein domain that binds to the DNA

If a frameshift mutation causes a stop codon to be inserted into the coding region of a DNA sequence, then ____________.

the resulting protein will be shortened and is often nonfunctional

When both glucose and lactose are present.....

the transcription rate is very, very slow.

Two protein complexes that communicate the effects of regulatory transcription factors are _____________________ and ________________.

transcription factor IID (TFIID) and mediator.

Eukaryotic genomes have many copies of genes H1, H2A, H2B, and H3, but some copies have accumulated mutations and are called histone ____________.

variants