Exam 4 Flashcards by Charlotte Schrimsher

Which are regulatory proteins and which are small effector molecules?

Regulatory= activators and repressors
Small effector=inducers, inhibitors,corepressors

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A repressor is a _____ that ______ transcription
A. Small effector, inhibits
B. Small effector, enhances
C. Regulatory protein, inhibits
D. Regulatory protein, enhances

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Which of the following combinations would cause the rate of 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

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Which genes are under the control of lac promote

Lac Z
Lac Y
Lac A

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

When allolactose is not bound to the repressor

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

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The active site of the lac repressor protein is composed of
A. The protein domain that binds to other lac repressors
B. The protein domain that binds to allolactose
C. A glucose binding domain
D. The protein domain that binds to DNA

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Which of the following best describes regulation of the lac operon?
A. Inducible under negative and positive control
B. Repressible under negative and positive control

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If a cell has a mutant lacY gene that produces a nonfunctional product, which statement is true?
A. The lac operon cannot be transcribed by RNA polymerase because of the lacY mutation
B. The lac operon cannot be induced because lactose cannot enter the cell
C. Expression of the lac operon is normal because lacY is not required to produce allolactose
D. The repressor cannot bind to the operator

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A regulatory protein that binds to DNA and inhibits transcription

Repressor

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A regulatory protein that increases rate of transcription

Activator

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Small effector molecule that causes transcription to increase

Inducer

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

Operon

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A sequence of bases that signals the beginning of transcription

Promoter

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

Operator

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If an E. coli cell is exposed to glucose, what happens?
A. cAMP levels are decreased which does not allow the CAP protein to bind to its regulatory region
B. cAMP levels are increased and transcription of lac operon is decreased due to lack of CAP protein binding to its regulatory region

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

lacO

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Which is not a part of the lac operon

lacI

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The lac repressor is inactivated by what?

Allolactose

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T or F
The lac repressor is active in the absence of lactose within the cell?

True

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cAMP is low, CAP does not bind to the activator binding site and transcription is turned off when glucose is or isn’t present?

Is present

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The lac repressor binds to what? And does what?

Binds to operator
Prevents transcription

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Is transcription rate high or low when both glucose and lactose are present?

Very low

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T or F
In absence of glucose, and in presence of lactose, allolactose binds to repressor, allowing RNA polymerase to carry on transcription

True

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T or F When both glucose and lactose are absent the highest rate of transcription occurs?

False

T or F The polycistronic mRNA is transcribed from the lac operon when lactose is present in the cell and glucose is not present at

True

Regulatory transcription factors can be modulated by A. The binding of small effector proteins B. Protein protein interactions C. Covalent modifications D. All of the above

What are two ways histone modifications may alter chromatin structure

Interactions between histones and DNA Binding of proteins to chromatin

Why is an NFR needed at core promoter for transcription to occur?

So transcription factors can recognize enhancers and pre initiation complex can form

Why is histone eviction needed for elongation phase?

Because RNA polymerase 2 can’t transcribe through nucleosomes

A chromatin remodeling complex may A. Change location of nucleosomes B. Evict histones from DNA C. Replace standard histones with histone variants D. All of the above

According to the histone code hypothesis, the pattern of histone modifications acts like a language that A. Influences chromatin structure B. Promotes transcriptional termination C. Inhibits elongation of RNA polymerase D. All of the above

Which of the following characteristics is typical of eukaryotic gene that can be transcribed A. core promoter is wrapped around a nucleosome B. Core promoter is found in nucleosome free region C. Terminator is wrapped around a nucleosome D. None of the above

Transcriptional activation of eukaryotic genes involves which of the following events? A. Changes in nucleosome location B. Change in histone composition C. Histone modifications D. All of the above

Which amino acids are acetylated in histones

Lysine

Activators bind to what type of DNA sequence?

Enhancers

Which of the following is not a common post-translational modification that occurs in histones? A. Acetylation B. Methylation C. Phosphorylation D. Glycosylation

Nucleosome-free regions A. Always contain an enhancer B. Are always only associated with genes that are being actively transcribed C. Are found flanking many actively transcribed genes in eukaryotes D. Always contain a transcriptional start site

What is the result when the core histones are acetylated via histone acetyltransferase A. DNA becomes less associated with the core B. DNA becomes more tightly associated with the core

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

Histone code hypothesis

Enzymes which acetylate the positively charged lysines with the core histone proteins

Histone acetylation

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

DNA methylation

Proteins which bind methylated sequences

Methyl-CpG-binding proteins

The methylation of DNA that was previously unmethylated

De novo methylation

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

Maintenance methylation

Combinatorial control of transcription factors refers to the phenomenon that A. Transcription factors always combine with each other when regulating genes B. Small effector molecules and regulatory transcription factors are found in many different combinations C. Combination of many factors determines the expression of any given gene

Glucocorticoid hormones activate genes that are involved in which of the following processes? A. Synthesis of glucose B. Mobilization of days C. Breakdown of proteins D. All of the above

Glucocorticoids are _____ hormones secretes by _____ glands

Steroid Endocrine

Arrange the following in the proper order in which they occur during glucocorticoid hormone action 1. Binding of hormone to receptor 2. Release of HSP90 proteins 3. Entry of hormone into nucleus

1,2,3

In eukaryotes, methyl groups are added to the ____ residuals

Cytosine

The enzymes that add the methyl group are known as

DNA methyltransferases

Methylation usually results in the ____ of transcription

Inhibition

The residues that precedes the ____ genes are not typically methylated

Housekeeping

In DNA replication, the methylation pattern is ____

Heritable

The most common form of methylation is ____

Maintenance methylation

T or F Glucocorticoid response elements function as enhancers

True

T or F The glucocorticoid receptor is active as a dimer

True

T or F Frameshift mutations can be read in multiples of 3

False, only multiples of 1 and 2

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

None

Cells that give rise to gametes

Germ line cells

Mutation that can be passed onto offspring

Germ line mutation

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

Somatic cells

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

Genetic mosaic

The nucleic acid sequence in mRNA is determined by A. The order of amino acids in proteins B. Nucleotide sequence in DNA C. Nucleotide sequence in tRNA D. All of the above

If a gram shift mutation causes a stop codon to be inserted into the coding region of the DNA sequence, then… A. The resulting protein will be lengthened by one amino acid but will likely retain its original function B. The resulting protein will be shortened and is often nonfunctional C. The phenotype will change but not the genotype D. The resulting protein will not be affected

A nucleotide deletion in DNA replication… A. Causes one amino acid of the protein to be incorrect B. Has no effect on resulting protein C. Causes amino acid downstream from deletion to be incorrect D. Causes all of amino acids of protein to be incorrect

T or F The addition of a single nucleotide to the DNA sequence causes a frameshift mutation

True

T or F In a frameshift mutation all of the amino acids before the shift are changed

False

Effect of mutation May increase or decrease rate of transcription

Promoter

Effect of mutation May disrupt the ability of the gene to be properly regulated

Operator

Effect of mutation May alter the ability of mRNA to be translated or alter its stability

5’-UTR/ 3’-UTR

Effect of mutation May alter ability of pre-mRNA to be properly spliced

Splice site

A ____ is a change in a single base pair within the DNA

Point mutation

What features of this pedigree indicate autosomal recessive inheritance

Neither parent affected by disease but offspring is

What features of pedigree indicate autosomal dominant inheritance?

Both/ one parent affected by disease

What features of pedigree indicate X-linked recessive inheritance?

All affected individuals are male

A mutant gene that promotes cancer when it is over expressed is called A. A tumor suppressor gene B. An oncogene C. Both a and b

An unaffected couple has two children, one normal and one with CF. What is the probability that the normal child is a carrier?

2/3

A phenotypically normal individual with a sibling that has CF married a known carrier of the CF mutation. What’s probability their child will have CF?

1/6

A _____ is a normal cellular gene that through a _____ mutation becomes an oncogene

Proto-oncogene Gain of function

Mutated forms of the Rb protein A. Bind to E2F have no effect on cell division B. Bind to E2F thereby inhibiting cell division C. Do not bind to the E2F thereby promoting uncontrolled cell division D. Do not bind to E2F thereby inhibiting cell division

The protein ____ checks for damaged DNA thereby acting as quality control for the cell

p53

The term locus heterogeneity refers to disease that can be caused by mutations in _____

More than one gene

Locus heterogeneity may make it _____ to interpret pedigrees

More difficult

A loss of function mutation in what type of gene can lead to cancer?

Tumor suppressor

Silencing of tumor suppressor genes by DNA methylation in cancer is an example of what kind of change

Epigenetic

T or F The protein p21 keeps cyclin and cyclin-dependent kinase from binding to each other

True

What features of pedigree indicate x-linked dominant?

Only females exhibit trait since it’s lethal to males

T or F Methylation can inhibit the binding of activator proteins

True

How are operon different from regular genes?

Expression is done as a single unit

Encodes enzyme B-galatosidase (cleave galactose and glucose). Also converts small amount of lactose into allolactose

LacZ

Encodes lactose permease, the membrane protein required for active transport of lactose into cytoplasm of bacterium

LacY

Encodes galactoside transactelyate, an enzyme that covalently modify a lactose and prevents lactose analog buildup

LacA

Responsible for transcription of lacY, Z, A gene as a single unit

LacP (lac promoter)

Sequence of DNA that is recognized by activator protein CAP

CAP site

Sequence of bases that provides a binding site for repressor protein

LacO (operator site)

Encodes lac repressor and isn’t part of lac operon

LacL

Binds to repressor which prevents it from binding to operator site so RNA polymerase 2 can transcribe operon

Allolactose

What are the negative control mechanisms for gene regulation in bacteria

Repressor protein= (lacI) Effector molecule= allolactose

Positive control mechanism for gene regulation in bacteria

Activator protein= CAP effector molecule= cAMP

What if there is no lactose, is glucose? Rate of transcription? Effector molecule lactose and cAMP present?

Very low Lactose and cAMP not present

What if lactose and glucose present? Rate of transcription? Effector molecule lactose or cAMP present?

Low Lactose present, cAMP not

What if no lactose, no glucose? Rate of transcription? Are effector molecules lactose and cAMP present?

Very low Lactose not present cAMP present

What if lactose present, glucose not? Rate of transcription? Effector molecules lactose and cAMP present?

High transcription Both present

Does acetylation increase or decrease transcription?

Increade

Does methylation increase or decrease transcription?

Increase OR decrease

Does phosphorylation increase or decrease transcription?

Increase

Base substitutions where amino acid does change, can have huge affect on phenotype and cause serious diseases

Missense mutation (neutral mutation)

A change from one codon that specifies an amino acid to a stop codon which terminates translation earlier than normal

Nonsense mutation

Don’t alter amino acid sequence even though bar has changed

Silent mutation

Addition of deletion of number of nucleotides that is not divisible by 3

Frameshift mutation

Exam 4 Flashcards

(111 cards)