Genetics Topic 6

"Operon," a term coined in the early 1960s, is defined as a) a set of genetic operations. b) the initiation and termination regions of a gene. c) regulatory loci. d) A segment of DNA consisting of several genes acting as a transcriptional unit.

A segment of DNA consisting of several genes acting as a transcriptional unit.

An enhancer element is a) a specific nucelotide sequence in DNA b) a regulatory protein c) an mRNA-degrading enzyme d) an mRNA transcript

A) a specific nucelotide sequence in DNA

For a given gene, HREs are located a) in the promoter sequence b) immediately after the start site of transcription c) in an enhancer element d) in the termination sequence

A) in the promoter sequence

What is the difference between inducible and repressible operons? give an example of each.

An inducible operon,the presence of a small effector molecule causes transcription to occur .In repressable operons, a small eefector molecule inhibits transcription. the effects of these small molecules are mediated through regulatory proteins that bind to the DNA.Repressible operons usually encode anabolic enzymes and inducible operons encode catabolic enzymes.

5-methylcytosine is most often found associated with which DNA sequence a) ATTA b) CG c) ACT d) AC

B) CG

A hormone is a a) repressor b) effector c) activator d) enhancer

B) effector

The mammalian immune system can produce billions of different antibodies. This tremendous gene product diversity is produced by a) an equal number of antibody genes b) exon shuffling c) post-translational modification d) large multi-gene families

B) exon shuffling

Transcriptionally active genes have ____ level of DNA methylation when compared to methylation of inactive genes a) higher b) lower c) the same d) no

B) lower

Gene expression in eukaryotes is regulated at the level of a) transcription b) processing c) translation d) all of the above

D) all of the above

mRNA-level control of gene expression can be accomplished by regulating a) movement or transport of mRNA transcripts b) translation rate of mRNA transcripts c) longevity of mRNA transcripts d) all of the above

D) all of the above

Points of control in eukaryotic gene expression Points of control in eukaryotic gene expression include RNA processing. translation. transcription. post-translation.

RNA processing. translation. transcription. post-translation.

Deletion of glucocorticoid response elements (GREs) What is the expected result if the glucocorticoid response elements (GREs) were deleted in the region upstream of a gene? Picture The gene would be activated all the time, even in the absence of glucocorticoid Glucocorticoids would still be required to activate the gene The GR would no longer be able to move into the nucleus The gene could no longer be activated in response to glucocorticoid The GR would no longer be able to bind to glucocorticoid

The gene could no longer be activated in response to glucocorticoid

Repressor function in lac and trp operons of E. coli In both the lac and trp operons of E. coli, a repressor binds to an operator to block transcription. Identify the most accurate description of these operons. The operator is a small molecule that binds the repressor (as a co-repressor) The trp operon is repressible while the lac operon is inducible Both operons are considered repressible Both operons are considered inducible The trp operon is inducible while the lac operon is repressible

The trp operon is repressible while the lac operon is inducible

The various kinds of human hemoglobin are made up of polypeptide chains encoded by __________, the elements of which are up- and down-regulated at different points in development. a pair of genes a single gene with many exons a myoglobin gene multigene families

a pair of genes

In a Plac- (promoter mutant) strain of E. coli growing in medium containing lactose, the bacteria a) have the ability to metabolize lactose. b) produce normal quantities of enzyme, but they are inactive. c) do not synthesize the enzymes necessary for lactose metabolism. d) will not survive.

a) have the ability to metabolize lactose.

Which of the following would be the gene product of a constitutive gene? DNA polymerase RNA polymerase ATP synthetase all of the above

all of the above

When allolactose binds to the repressor, a(n) ___ occurs which inactivates the repressor protein. mutation allosteric shift repressible effect derepressism

allosteric shift

What type of regulatory transcription factor binds DNA and increases the transcription of a gene? a repressor exerting negative control a repressor exerting positive control an activator exerting negative control an activator exerting positive control a combination of both a repressor and activator exerting negative control

an activator exerting positive control

A regulatory element that can function from a large distance (e.g. tens of thousands of base pairs) from a promoter is called an inducer. a repressor. an enhancer. a core promoter. a histone.

an enhancer.

which of the following is not a form of gene regulation in bacteria? a. transcriptiomal b. RNA processing c. Translational d. post-translational e. All of the above are levels at which bacteria are able to regulate gene expression.

b. RNA processing

The developmental trajectory of an undifferentiated stem cell - its fate - is established genetically in a process called fating. determination. potentiation. commitment.

determination.

A molecule that has a regulatory role in operon function is generally termed a(n) _______ molecule. regulatory coordinator effector aporepressor

effector

A great many of the 25,000 or so genes in the human genome are likely to be regulatory genes. That is, they help orchestrate the developmental cascade that ensues after fertilization. In general, what do such genes encode? structural proteins transcription factors enzymes ribosomal RNA

enzymes

In the lac operon, the gene that encodes the β-galactosidase enzyme is lacA. lacZ. lacY. lacO.

lacZ

Identify the correct order of expression of the following genes or gene types that play a role in Drosophila development: a) gap genes - bicoid - homeotic genes b) maternal effect genes - homeotic genes - segmentation genes c) maternal effect genes - segmentation genes - homeotic genes d) homeotic genes - pair-rule genes - bicoid

maternal effect genes - segmentation genes - homeotic genes

In bacteriophage λ, the product of the cI gene is a(n) inducer. repressor. activator. corepressor.

repressor

Dosage compensation in mammals is achieved by ___________, while that in fruit flies is achieved by a) silencing genes on one of the X chromosomes in females; upregulating the X chromosome genes of males. b) upregulating the X chromosome genes of males; silencing genes on one of the X chromosomes in females. c) upregulating the X chromosome genes of females; silencing genes on one of the X chromosomes in males. d) silencing genes on the X chromosome in males; upregulating the X chromosome genes of females.

silencing genes on one of the X chromosomes in females; upregulating the X chromosome genes of males.

The process of attenuation in the trp operon involves a) temporary mRNA secondary loop structures that slow or stall translation. b) slow depletion of tryptophan. c) depletion of RNA polymerase. d) production of trp attenuator proteins.

temporary mRNA secondary loop structures that slow or stall translation.

The event that occurs when allolactose levels increase in E. coli is transcription of genes within the lac operon increases. transcription of genes within the lac operon decreases. transcription of genes within the lac operon does not change. E. coli cells replicate rapidly. the tryptophan operon becomes more active.

transcription of genes within the lac operon increases.

The molecule that functions as a corepressor for the trp operon is glucose. cAMP. tryptophan. CAP. lactose.

tryptophan.

Which of the following represents the general structure of an inducible gene? a) (promoter)-(operator)-(coding sequence)-(terminator) b) (operator)-(promoter)-(coding sequence)-(terminator) c) (terminator)-(coding sequence)-(operator)-(promoter) d) (coding sequence)-(promoter)-(operator)-(terminator)

(promoter)-(operator)-(coding sequence)-(terminator)

Cells possessing the ability to develop or differentiate into any cell (tissue) type are said to be totipotent. plastic. undifferentiated. immature.

totipotent

The event that occurs in E. coli when lactose is absent from its environment is large amounts of b-galactosidase, lactose permease, and galactoside transacetylase are made. trace amounts of b-galactosidase, lactose permease, and galactoside transacetylase are made. no b-galactosidase, lactose permease, and galactoside transacetylase is made. the lac operon is induced. polycistronic mRNA levels would be very high.

trace amounts of b-galactosidase, lactose permease, and galactoside transacetylase are made.

In eukaryotic cell, when a positive regulatory protein interacts with a promoter element a) transcription is activated b) transcription is inhibited c) translation is inhibited d) replication is activated

A) transcription is activated

In prokayryotes, gene regulation occurs primarily at the ___ level a) transcriptional b) post-transcriptional c) translational d) post-translational

A) transcriptional

Transcription factors and regulatory substances are generally a) enzymes b) DNA elements c) DNA binding proteins d) inducers

C) DNA binding proteins

DNA that is bound to histone proteins a) contains the most actively transcribed genes b) is hypersensitive to DNase I c) cannot be transcribed d) is targeted for destruction by nucleases

C) cannot be transcribed

In the absence of galactose, the GAL genes are a) transcribed and translated b) transcribed but not translated c) neither transcribed or translated d) constitutively expressed

C) neither transcribed or translated

Factors that alter gene expression Factors that can alter the level of expression of a gene include an increase in environmental temperature. an increase in salinity. exposure to UV radiation. presence of a particular energy substrate.

an increase in environmental temperature. an increase in salinity. exposure to UV radiation. presence of a particular energy substrate.

Foreign elements in the body that elicit an immune response are _________, while the molecules manufactured to neutralize those elements are antibodies; antigens. antigens; antibodies. antibodies; allergens. B-cells; T-cells.

antigens; antibodies.

In a cell with a lacOc mutation, the operon genes will only be expressed in the presence of lactose. not be expressed in the presence of lactose. not be expressed in the absence of lactose. be expressed in the presence or absence of lactose.

be expressed in the presence or absence of lactose.

Genes that are expressed at all times at relatively constant levels are known as ____ genes. a. inducible b. repressible c. positive d. constitutive e. structural

d. constitutive

DNA methylation in many eukaryotic organisms usually causes a. increased translation levels b. decreased translation levels c. increased transcription levels d. decreased transcription levels e.introns to be removed.

d. decreased transcription levels

The regulatory substance that brings about gene expression in an inducible operon is called the repressor. co-repressor. inducer. co-inducer.

inducer

Sex determination in mammals is controlled by which key gene? testis-determining factor gene (TDF) ovary-determining factor gene (ODF) androgen factor gene (AF)

testis-determining factor gene (TDF)

Immunoglobulin molecules consist of two heavy (H) and two light (L) polypeptide chains. Antigen binding specificity is conferred by the amino acid sequence of the L chains. the N-terminal half of the H chains. the first two domains of the H chains. the N-terminal domains of both chains.

the N-terminal domains of both chains.

In an inducible operon, the genes are always expressed. usually not expressed unless a signal turns them "on." usually expressed unless a signal turns them "off." never expressed.

usually not expressed unless a signal turns them "on."

The segmentation genes of insects, responsible for differentiation into body regions (head, thorax, and abdomen) and segments of those regions, have highly similar homologs in vertebrates. Yet, vertebrates do not have the obvious segmentation of insects. Where is segmentation most evident in vertebrates? skull structure organ arrangement vertebral column limb structure

vertebral column

Which enzymes will be produced in a cell in which there is a nonsense mutation in the lacY gene? β-galactosidase lactose permease transacetylase all of the above

β-galactosidase

The Gal4 protein in yeast interacts with DNA at a regulatory site upstream of the GAL genes. Its DNA binding domain is a a) leucine zipper b) gene activator c) zinc finger d) inducer

C) zinc finger

The motif of the DNA binding domains of most SHRs is usually a a) leucine zipper b) gene activator c) zinc finger d) inducer

C) zinc finger

______________ refers to the process by which elements of different immunoglobulin genes rearrange to provide a diversity of transcripts (and thus the diversity of antibodies). Transcript processing Crossing over Somatic recombination Post-translational modification

Somatic recombination

Function of the trp operon in E. coli The trp operon of E. coli controls expression of five enzymes that are involved in the biosynthesis of the amino acid tryptophan. A trp repressor protein (trpR) binds to the trp operator to prevent transcription when tryptophan is present. When would the tryptophan synthesis enzymes be made if the trpR gene was mutated? Picture In the presence of lactose Only when tryptophan was present Only when tryptophan was absent The enzymes would never be made because the repressor would not bind DNA The enzymes would be made in the presence or absence of tryptophan

The enzymes would be made in the presence or absence of tryptophan

In a lacI- strain of E. coli, the lac operon will be expressed only in the presence of lactose. only in the absence of lactose. both in the presence or absence of lactose. not at all

both in the presence or absence of lactose.

When cultures of E. coli are grown in the presence of lactose and glucose, the lac operon is under ___ control. positive negative both positive and negative neither positive or negative

both positive and negative

Homeoboxes are a) collections of homeotic mutants. b) untranscribed regulatory regions of developmental genes. c) conserved coding sequences about 180 bp in length found in homeotic genes. d) part of a general class of developmental mutants.

c) conserved coding sequences about 180 bp in length found in homeotic genes.

Transcription factors that bind to DNA and stimulate transcription are a. repressors b. small effector molecules c. activators d. promoters e. operators.

c. activators

Genes organized into an operon are beneficial to certain bacteria because the operon allows for differential regulation of individual genes that encode proteins with a common function. coordinated regulation of a group of genes that encode proteins with a common function. separate regulation of individual genes that encode proteins with different functions. coordinated regulation of a group of genes that encode proteins with different functions. coordinated regulation of a group of proteins involved in numerous cellular activities.

coordinated regulation of a group of genes that encode proteins with a common function.

In bacteriophage lambda, the lytic pathways are followed if the product of the ___ gene dominates. cI N cro Q

cro

The catabolite activator protein (CAP) binds to the ___ protein to regulate expression of the lac operon. promoter repressor cyclic AMP inducer

cyclic AMP

the presence of ______ in the medium prevents CAP from binding to the DNA, resulting in ____ in transcription of the lac operon a. lactose, an increase b. glucose, an increase c. cAMP, a decrease d. glucose, a decrease e. lactose, a decrease

d. glucose, a decrease

Which of the following are not steps in the X-chromosome inactivation process? selection of inactivated X chromosome inactivation of testis-determining factor gene chromosome counting X-inactivation

inactivation of testis-determining factor gene

The lac operon is inducible and under negative control. repressible and under both positive and negative control. inducible and under both positive and negative control. repressible and under negative control.

inducible and under both positive and negative control.

DNA methylation increases transcription. inhibits transcription. increases crossover events. decreases crossover events. promotes post-translational modification of proteins.

inhibits transcription.

An mRNA that contains the coding sequence for multiple genes An mRNA that contains the coding sequence for two or more structural genes is called a polyintronic mRNA. polyextronic mRNA. polycistronic mRNA. polyexpressive mRNA. polyrepressor mRNA.

polycistronic mRNA.

What is the function of the general transcription factor The general transcription factor TFIID recognizes the enhancer. recognizes the TATA box. recognizes the silencer. transcribes mRNA. is a silencer.

recognizes the TATA box.

The trp operon is considered___ operon because the structural genes necessary for tryptophan synthesis are not expressed when the levels of typtophan in the cell are high a. an inductible b.positive c. a repressible d. a negative e. both c and d are correct

c. a repressible

For the lac operon, what would be the expected effects of a mutation in the operator site that prevented the binding of the repressor protein? a. the operon would always be tured on. b. the operon would always be turned off. c. the operon would always be turned on,except when glucose is present. d. the operon would be turned on only in the presence of lactose. e. the operon would be turned on only in the presence of lactose and the absence of glucose.

c. the operon would always be turned on,except when glucose is present.

Liver cells, mammary cells, and skin cells all contain the same genome; however, their respective proteomes vary drastically. This observation is best explained by what phenomenon? gene splicing cell division cell differentiation crossing over evolution

cell differentiation

What kinds of experiments demonstrate "DNA constancy," in which development does not entail a loss of genetic information, only differential expression of information available in all cells? hydridization experiments cloning experiments fate map experiments stem cell experiments

cloning experiments

Some genes are expressed at a constant level Genes expressed at relatively constant levels in tissues regardless of variations in the animal's condition are called a transposable element. steady state gene. constitutive gene. recombinant gene. multifunctional gene.

constitutive gene.

Cellular ability to control gene expression A cell's ability to control their level of gene expression is called gene transformation. gene regulation. gene splicing. gene addition. gene correction.

gene regulation.

The core promoter in eukaryotes is usually The core promoter in eukaryotes is usually composed of which two features? transcriptional start site and enhancer transcriptional start site and response elements transcriptional start site and TATA box enhancer and TATA box response elements and TATA box

transcriptional start site and TATA box

Identify the correct order of events: Fertilization - induction - determination - differentiation Fertilization - determination - induction - differentiation Differentiation - fertilization - induction - determination Induction - differentiation - determination - fertilization

Fertilization - determination - induction - differentiation

What inference about underlying genetic structure can you draw from the occurrence of mutations like antennapedia, where a leg develops in the place of antennae? a) Extensive recombination occurs in such mutants. b) Genes for antennae are identical to those for legs in such organisms. c) There is extensive homology between the genes of such structures, probably pointing to a common origin. d) Genes for the two structures are convergently similar owing to selection for similar patterns of segmentation.

c) There is extensive homology between the genes of such structures, probably pointing to a common origin.

______ refers to the phenomenon where a single type o pre-mRNA may give rise to multiple types of mRNAs due to different patterns of intron and exon removal. a. spliceosomes b. variable expression c. alternative splicing d.polycisteonic mRNA e. induced silencing

c. alternative splicing

in bacteria, the unit of DNA that contains multiple genes under the control of a single promoter is called____. The mRNA produced from this unit is referred to as ___mRNA a. an operator, a polycistronic b. a template, a structural c. an operon, a polycistronic d. an operon, a monocistronic e. a template, a monocistronic

c. an operon, a polycistronic

regulatory elements that function to increase transcription levels in eukaryotes are called a. promoters b.promoters c. enhancers d. transcriptional start sites e.activators

c. enhancers

The major difference in gene regulation between prokaryotes and eukaryotes is eukaryotic and prokaryotic genes are usually grouped for common functions. Eukaryotic genes regulation requires fewer signals that prokaryotic gene regulation. Eukaryotic gene regulation is more simplistic than prokaryotic gene regulation. Eukaryotic genes are arranged individually, while prokaryotic genes are grouped into operons. Eukaryotic gene regulation tends to require less coordination and integration than prokaryotic gene regulation.

Eukaryotic genes are arranged individually, while prokaryotic genes are grouped into operons.

In 1997, Dolly the sheep became the first successfully cloned mammal. The cloning procedure basically entailed isolating DNA from somatic cells, injecting it into enucleated egg cells (oocytes), and implanting the resulting embryos into a surrogate mother. isolating two different types of somatic cells, fusing them, and implanting the resulting embryo into a surrogate mother. fusing somatic cells with enucleated egg cells (oocytes) and implanting the resulting embryos into surrogate mothers. fusing two egg cells, one of which had previously had its nucleus removed, followed by implantation into a surrogate mother.

fusing somatic cells with enucleated egg cells (oocytes) and implanting the resulting embryos into surrogate mothers.

You isolate a Drosophila mutant with antennae developing where the legs should be. This is an example of a(n) segmentation mutation. homeotic mutation. bicoid mutation. gap-gene mutation.

homeotic mutation.

Which of the following has the lowest developmental potential? embryonic stem cell zygote liver cell All of the above have equal developmental potential.

liver cell

Small effector molecules cause a conformational change in a regulatory protein. can prevent a repressor from binding a gene region. regulate gene transcription by binding to DNA. regulate gene transcription by binding a regulatory protein.

regulate gene transcription by binding a regulatory protein.

Transcriptionally active regions of DNA are a) complexed with histone proteins b) sensitive to digestion with DNase I c) heavily methylated d) resistant to digestion with DNase I

B) sensitive to digestion with DNase I

In plant cells, gibberellin a) inhibits gene expression b) stimulates transcription c) limits transcription d) has no effect on gene expression

B) stimulates transcription

In a Drosophila zygote the ratio of X chromosomes to autosome sets is 0.5. This zygote will develop into a(n) male. female. intersex individual. none of the above - this ratio has nothing to do with sex determination

male.

When the gene product of the lacI gene is present in bacterial cells grown in the presence of lactose repressor protein will bind to the lac operator region. β-galactosidase will not be produced. the genes in the lac operon will be transcribed. the cells will be unable to catabolize lactose.

the genes in the lac operon will be transcribed

DNase I hypersensitive regions are usually located a) upstream from the start site of transcription b) in the middle of a gene near intron splice sites c) downstream from the promoter d) in telomeric or centromeric regions

A) upstream from the start site of transcription

Peptide hormones bind _____, while steroid hormones bind _____ a) with target cells in the cell membrane; with receptors in the cell nucleus b) with receptors in the nucleus; with other steroids c) to DNA recognition sequences; to mRNA recognition sequences d) in plant cells; in animal cells

A) with target cells in the cell membrane; with receptors in the cell nucleus

A particular strain of E. coli is lacOc, lacZ+ and Ylac-. In the absence of lactose, which enzyme(s) will be produced in this cell? a) β-galactosidase only b) β-galactosidase and lactose permease c) β-galactosidase, lactose permease, and transacetylase d) None of the enzymes will be produced.

β-galactosidase only

Genomes of eukaryotes contain many defunct or non-functional genes, generally rendered defective by mutations of their promoter regions. These are known as a) ex-genes b) pseudogenes c) pre-genes d) nonsense genes

B) pseudogenes