Chapter 12: Control of Gene Expression (MC Questions)

What structural element that is inserted into the major groove of DNA, where it recognizes specific DNA base pair sequences lining the groove, appears to be common to many DNA-binding motifs? A. An α-helix B. Aβ-pleated sheet C. A double helix D. A random coil

A. An α-helix

What allows a glucocorticoid receptor to enter and be retained by the nucleus? A. Binding of a glucocorticoid causes the receptor to change shape and may expose a nuclear localization signal. B. Binding of a glucocorticoid denatures the receptor allowing it through the nuclear pores. C. The receptor follows the glucocorticoid into the nucleus. D. The glucocorticoid attaches a nuclear localization signal to the receptor

A. Binding of a glucocorticoid causes the receptor to change shape and may expose a nuclear localization signal.

A site of indentation on the surface of a chromosome to which the mitotic spindle attaches? A. Centromere B. Centrosome C. Centriole D. Telomere

A. Centromere

The region stretching from roughly the TATA box to the transcription start site is called the ____. A. Core promoter B. Initiator C. Starter D. Operator

A. Core promoter

What technique below provides the most direct evidence of widescale transcriptional level control? This technique allows the expression of thousands of genes to be monitored in a single experiment. A. DNA microarrays B. 2-dimensional gel electrophoresis C. Affinity chromatography D. Intelligent chips

A. DNA microarrays

Specific transcription factors often bind to DNA at sites flanking the gene they affect. These sites are called _________. A. Enhancement sites B. Response elements C. Respondents D. Correspondents

A. Enhancement sites

What RNA sequences, located within exons whose inclusion is regulated, control the recognition and use of weak splice sites? A. Exonic splicing enhancers B. Intronic splicing enhancers C. Exonic splicing inducers D. Exonic spicing inhibitors

A. Exonic splicing enhancers

Which type of molecule binds at the core promoter sites in association with RNA polymerase? A. General transcription factors B. Sequence-specific transcription factors C. Elongation factors D. Initiation factors

A. General transcription factors

Certain genes are either active or inactive during early mammalian development depending entirely on whether they came from the sperm or the egg. What is the name of this phenomenon? A. Genomic imprinting B. Genomic establishment C. Genomic implantation D. Inculcation

A. Genomic imprinting

The hypothesis, which postulates that the activity of a particular region of chromatin depends upon specific modification to the histone tails in that region, is known as the _______. A. Histone code. B. Lyon hypothesis. C. Boundary element. D. None of these is the correct answer.

A. Histone code

In the lac operon, lactose functions as the _______. A. Inducer B. Operator C. Repressor D. Co-repressor

A. Inducer

What kind of bond forms between the phosphate groups of the DNA backbone and the positively charged amino acid residues of the histones and helps to hold the molecules together? A. Ionic bonds B. Disulfide linkages C. Van der Waals forces D. Polar and nonpolar covalent bonds

A. Ionic bonds

What is a function of the nuclear lamina? A. It provides mechanical support for the nuclear envelope. B. It provides mechanical support for the nuclear envelope. C. It serves as an attachment site for chromatin fibers at the nuclear periphery. D. It provides mechanical support for the nuclear envelope and it provides mechanical support for the nuclear envelope.

A. It provides mechanical support for the nuclear envelope.

The length of the poly(A) tail is related to what property? A. Messenger RNA longevity B. The time it takes to synthesize one protein C. The size of the ribosome D. Initiation and termination of transcription

A. Messenger RNA longevity

How does the transport mechanism for mRNAs ensure that only mature mRNAs can be transported to the cytoplasm? A. Messenger RNAs with one or more unspliced introns are retained in the nucleus. B. Messenger RNAs with a poly(A) tail are retained in the nucleus. C. Messenger RNAs without the full 5'-methylguanosine are stabilized. D. Messenger RNAs with one or more spliced introns are retained in the nucleus.

A. Messenger RNAs with one or more unspliced introns are retained in the nucleus.

_________ refers to the circumstance when the binding of a protein to DNA is required for gene expression. A. Positive control B. Negative control C. Averaged control D. Circumspect control

A. Positive control

Contrary to the plasma membrane, the nuclear envelope __________. A. Prevents passage of macromolecules B. Allows passage of macromolecules C. Prevents passage of proteins D. None of these is the correct answer.

A. Prevents passage of macromolecules

DNA polymerases do not initiate DNA synthesis; they can only add DNA to the 3' end of an existing strand using the complementary strand as a template. The strand with the free 3'-end to which the DNA polymerase adds new nucleotides is called a(n) ________. A. Primer B. Strand C. Starter D. Primmer

A. Primer

An unusual stretch of repeated sequences at the tips of a DNA molecule forming a cap at each end of the chromosome is called a ________. A. Telomere B. Chromomere C. Centromere D. Karyomere

A. Telomere

What domain of a transcription factor is responsible for recognizing and associating with specific DNA base pair sequences? A. The DNA-binding domain B. The activation domain C. The repression domain D. The DNA-unwinding domain

A. The DNA-binding domain

Once an X chromosome has been inactivated in a cell, what happens to the corresponding X chromosome in all of that cell's descendants? A. The corresponding X chromosome will be inactivated in all of the descendants of that cell. B. The corresponding X chromosome will not necessarily be inactivated in all of the cell's descendants. C. The corresponding X chromosome will be activated in all of the descendants of that cell. D. The other X chromosome will be inactivated in the descendants of the cell.

A. The corresponding X chromosome will be inactivated in all of the descendants of that cell.

What discovery provided a crucial link between histone acetylation, chromatin structure and gene activation? A. The discovery that coactivators often had histone acetyltransferase activity B. The discovery that coactivators often add acetyl groups to DNA C. The discovery that nonhistone proteins can bind to histones D. The discovery that coactivators often remove acetyl groups from histones

A. The discovery that coactivators often had histone acetyltransferase activity

Which of the following determines the characteristic shape of mitotic chromosomes? A. The length of chromosome scaffold B. The thickness of the DNA C. The position of the centromere D. The position of the telomeres

A. The length of chromosome scaffold

What is the name of the site on the DNA that serves as a binding site for a repressor protein? A. The operator B. The terminator C. The promoter D. The structural genes

A. The operator

What happens to membrane proteins that have been attached to a single ubiquitin molecule? A. They are selectively incorporated into endocytic vesicles. B. They move immediately to proteasomes. C. They stay in the membrane. D. They move to the rough endoplasmic reticulum.

A. They are selectively incorporated into endocytic vesicles.

The z gene of the lac operon encodes ________. A. β-galactosidase B. α-galactosidase C. Thiogalactoside acetyltransferase D. Galactoside permease

A. β-galactosidase

How many X chromosomes are transcriptionally active in a female and male mammalian cell, respectively. A. 1, 1 B. 2, 1 C. 0, 1 D. 1, 2

B. 2, 1

What is used to further lengthen the 3' end of the overhanging strand after it has been initially made longer by telomerase? This enzyme returns the 5' end of the complementary strand to its previous length. A. A conventional RNA polymerase B. A conventional DNA polymerase C. Dnase D. DNA ligase

B. A conventional DNA polymerase

The success of cloning experiments led to the conclusion that _________. A. The transcriptional state of a differentiated cell is not irreversible B. A nucleus from a differentiated cell can be reprogrammed by factors residing in the cytoplasm of its new environment C. The transcriptional state of chromatin in a differentiated cell is not irreversible D. All of these are correct answers.

B. A nucleus from a differentiated cell can be reprogrammed by factors residing in the cytoplasm of its new environment

Chromatin that returns to the dispersed state after each mitotic division is called _______. A. Agranular chromatin B. Euchromatin C. Anabolic chromatin D. Heterochromatin

B. Euchromatin

Lactose is composed of _________ and ___________ linked together by a __________. A. Glucose, glucose, β-galactoside linkage B. Glucose, galactose, β-galactoside linkage C. Glucose, sucrose, peptide bond D. Glucose, galactose, α-galactoside linkage

B. Glucose, galactose, β-galactoside linkage

Which transcription factor motif is characterized by two α-helical segments separated by an intervening loop? A. Zinc finger motif B. Helix-loop-helix (HLH) motif C. HMG box motif D. Helix-turn-helix motif

B. Helix-loop-helix (HLH) motif

What happens to the trp operon repressor in the presence of tryptophan? A. It changes its conformation and is inactivated. B. It changes its conformation and is activated. C. It binds to DNA at the operator. D. It changes its conformation and is activated and it binds to DNA at the operator.

B. It changes its conformation and is activated.

What cells are known to have escaped normal growth control and thus keep dividing indefinitely? A. Liver cells B. Malignant cancer cells C. Nerve cells D. Kidney cells

B. Malignant cancer cells

What is the general name for the families of DNA-binding domains in transcription factors that have related structures that interact with DNA sequences? A. Architectures B. Motifs C. Milieus D. Constructs

B. Motifs

Isolated nuclei are treated with nonionic detergents and high salt, which remove lipids and nearly all of the histone and nonhistone proteins of the chromatin, the DNA is seen as a halo surrounding a residual nuclear core. If the DNA fibers are subsequently digested with DNase, the structure that remains possesses the same shape as the original nucleus but is composed of a network of thin protein-containing fibrils crisscrossing through the nuclear space. This insoluble fibrillar network has been named the ________. A. Nuclear framework B. Nuclear matrix C. Nucleofibrillar network D. Trabecular matrix

B. Nuclear matrix

A symmetrical sequence of DNA in which the two strands of DNA have the same 5' to 3' sequence is called a(n) _________. A. Response element B. Palindrome C. Aerodrome D. Velodrome

B. Palindrome

The irregular, fluorescently-labeled domains referred to as "speckles" that have been visualized in nuclei are associated with what cellular activity? A. Replication B. Pre-mRNA splicing C. Translation D. Reverse transcription

B. Pre-mRNA splicing

Which level of control of gene expression is defined as regulation of the path that the primary transcript follows as it is converted from pre-mRNA to mature mRNA? A. Transcriptional-level controls B. Processing-level controls C. Translational-level controls D. Replication-level controls

B. Processing-level controls

Which of the following is NOT found in a nucleosome? A. DNA B. RNA C. Histones D. RNA and histones

B. RNA

When a transcription factor has multiple zinc fingers as part of its DNA-binding site, why are they spaced at regular distances apart? A. To stretch out the DNA B. So they can project into successive major grooves in the target DNA C. So they constrict the DNA into the RNA polymerase active site D. So they can project into successive minor grooves in the target DNA

B. So they can project into successive major grooves in the target DNA

What is a telomere? A. Each arm of a chromosome. B. The cap at each end of a chromosome. C. The middle region of a chromosome. D. The nucleosome region of each chromosome arm.

B. The cap at each end of a chromosome.

Evidence suggests that miRNAs govern ___________. A. The processing of mRNAs B. The expression of batteries of genes that are involved in various cellular differentiation pathways C. The assembly of ribosomes D. DNA replication and repair

B. The expression of batteries of genes that are involved in various cellular differentiation pathways

If an exon is not supposed to be included in the mature mRNA, it must be excised. With what other RNA sequences is it excised? A. The flanking exons B. The flanking introns C. One flanking exon and one flanking intron D. the promoter and the poly(A) sequence

B. The flanking introns

If tryptophan is NOT present in a bacterial culture medium, which of the following statements is true? A. The cells contain the enzymes that synthesize tryptophan. B. The genes for the enzymes that synthesize tryptophan are repressed and the enzymes that synthesize tryptophan are not present. C. The genes coding for the enzymes that synthesize tryptophan are engaged in transcription. D. The cells contain the enzymes that synthesize tryptophan and the genes coding for the enzymes that synthesize tryptophan are engaged in transcription

B. The genes for the enzymes that synthesize tryptophan are repressed and the enzymes that synthesize tryptophan are not present.

What is probably the single most important distinction between prokaryotes and eukaryotes? A. The existence of the Golgi complex B. The separation of the cell's genetic material from the surrounding cytoplasm C. The existence of ribosomes D. The centrioles

B. The separation of the cell's genetic material from the surrounding cytoplasm

DNA microarrays can be used or may be used for which of the following purposes? A. To determine the degree of genetic variation in the human population B. To determine changes in the expression of genes during embryonic development, during the conversion of a normal cell into a malignant cell, and during cell division C. To identify alleles for particular genes that a person carries in their chromosomes D. All of these are correct answers.

B. To determine changes in the expression of genes during embryonic development, during the conversion of a normal cell into a malignant cell, and during cell division

What appears to be the purpose of the various motifs specialized for DNA-binding? A. To cut the DNA into the right shape for binding B. To provide a structurally stable framework on which specific DNA recognizing surfaces of the proteins can be properly positioned to interact with the double helix C. To facilitate the binding of rRNAs D. To unwind the double helix

B. To provide a structurally stable framework on which specific DNA recognizing surfaces of the proteins can be properly positioned to interact with the double helix

The proteins that orchestrate transcriptional control are referred to as __________. A. Translation factors B. Transcription factors C. Tfas D. Transductional factors

B. Transcription factors

Some splice sites can be bypassed by splicing machinery under certain conditions. What are such splice sites called? A. Bypass splice sites B. Weak splice sites C. Strong splice sites D. Soft splice sites

B. Weak splice sites

What is the packing ratio of DNA in mitotic chromosomes? A. 10:1 B. 7:1 C. 10,000:1 D. 1,000,000:1

C. 10,000:1

The average human cell has about ____ base pairs of DNA divided among ____ chromosomes for a diploid, unreplicated number of chromosomes. A. 6.4 billion, 23 B. 6.4 trillion, 46 C. 6.4 billion, 46 D. 64 billion, 46

C. 6.4 billion, 46

In what form do mRNAs and rRNAs usually move from the nucleus to the cytoplasm? A. As denatured molecules B. As compacted molecules C. As ribonucleoproteins D. Complexed with lipids

C. As ribonucleoproteins

Transcriptional activation A. Occurs at the level of RNA polymerase-mediated transcript initiation B. Occurs at the level of RNA polymerase-mediated elongation C. Can occur at the level of transcript initiation or elongation D. Does not occur. Only repression occurs

C. Can occur at the level of transcript initiation or elongation

Transcription factors bound at the enhancer stimulate the initiation of transcription at the core promoter through the action of intermediaries called _____. A. Corepressors B. Cotranscriptors C. Coactivators D. Costimulators

C. Coactivators

What type of chromatin serves to inhibit genetic recombination between homologous repetitive sequences, which can lead to DNA duplications and deletions? A. Facultative heterochromatin B. Facultative euchromatin C. Constitutive heterochromatin D. Constitutive euchromatin

C. Constitutive heterochromatin

Chromosomal aberrations, such as inversions and translocations, lead to human disease. Which of the following aberrations can result in gametes which possess additional copies of certain genes? A. Inversion B. Translocation C. Duplication D. All of the above

C. Duplication

DNA methylation is thought to serve as a(n) __________ mark or tag that allows identification of certain DNA regions and allows them to be used differently from other regions. A. Genetic B. Epinonomous C. Epigenetic D. Homologous

C. Epigenetic

A promoter and its enhancers are, in essence, "cordoned off " from other promoter/enhancer elements by specialized boundary sequences called _________. A. Cordoners B. Coactivators C. Insulators D. Blockers

C. Insulators

Scientists often stain chromosomes from mitotic cells and photograph the chromosomes in the microscope. Each chromosome is cut out of the photograph, the chromosomes are matched up in homologous pairs and they are placed in order of decreasing size. These pictures can be used to screen individuals for chromosomal abnormalities, like extra, missing or grossly altered chromosomes. What is such a picture called? A. Karyoplan B. Eukaryote C. Karyotype D. Karyokinesis

C. Karyotype

The thin filamentous meshwork within the nucleus that is bound by integral membrane proteins of the inner surface of the nuclear envelope in animal cells is called the _________. A. Basement lamina B. Basal lamina C. Nuclear lamina D. Nuclear limulus

C. Nuclear lamina

What is the general name of the approximately 30 proteins that comprise the nuclear pore complex? A. Porins B. Nucleorins C. Nucleoporins D. onnexins

C. Nucleoporins

Which of the following are NOT components of a typical bacterial operon? A. Promoter B. Repressor C. Nucleosome D. Structural genes

C. Nucleosome

Which of the traits below is characteristic of the classical nuclear localization signals? A. Possession of large numbers of hydrophobic amino acids B. Possession of one or two short stretches of negatively charged amino acids C. Possession of one or two short stretches of positively charged amino acids D. Twisted backbones

C. Possession of one or two short stretches of positively charged amino acids

The largest class of mammalian transcription factors contains which DNA-binding motif? A. The zinc finger motif B. The helix-loop/helix motif C. The leucine zipper motif D. The HMG box motif

C. The leucine zipper motif

What role do small, double-stranded RNAs similar to those involved in RNA interference play in inducing heterochromatization? A. They denature the DNA. B. They help to destroy an mRNA whose product triggers heterochromatization. C. They target a particular genome region for histone methylation and subsequent heterochromatization. D. They target a particular genome region for histone demethylation and subsequent heterochromatization

C. They target a particular genome region for histone methylation and subsequent heterochromatization.

Genes are physically moved to sites within the nucleus called _________, where the transcription machinery is concentrated and within which genes involved in the same response tend to become colocalized. A. Transcription homes B. Transcription sites C. Transcription factories D. Translation factories

C. Transcription factories

Covalent linkage to a small, highly-conserved protein called ________ marks proteins for destruction. A. Chaperonin B. Actin C. Ubiquitin D. Cyclin

C. Ubiquitin

The localization of mRNAs is mediated by specific proteins that recognize mRNA localization sequences on the mRNAs. What name has been given to these sequences? A. mRNA localizers B. Localicodes C. Zip codes D. Ziptrons

C. Zip codes

Which genetic phenomenon below involves the conversion of specific nucleotides to other nucleotides after RNA has been transcribed? A. Translational frameshifting B. Termination codon readthrough C. mRNA editing D. Alternative translation initiation

C. mRNA editing

Enhancers __________. A. Can be located at a significant distance from the genes that they regulate B. Can be moved experimentally from one place to another within a DNA molecule, without affecting the ability of a bound transcription factor to stimulate transcription C. Typically contain multiple binding sites for sequence-specific transcriptional activators D. All of these answers are correct

D. All of these answers are correct

Which of the following proteins binds to various regulatory sites of particular genes? A. Transcriptional repressors B. Sequence-specific transcription factors C. Transcriptional activators D. All of these answers are correct

D. All of these answers are correct

Which of the following is true of riboswitches? A. They bind a small metabolite like glucosamine or adenine with remarkable specificity. B. Once bound to a metabolite, these mRNAs undergo a change in their folded conformation. C. A small metabolite like glucosamine or adenine binds to a 5' noncoding region of the mRNA. D. All of these answers are correct.

D. All of these answers are correct.

Which of the following mechanisms is used as a translational level control of gene expression? A. Localization of mRNAs to certain sites within a cell B. Controlling whether or not an mRNA is translated C. Controlling the length of time that a mRNA is translated D. All of these answers are correct.

D. All of these answers are correct.

42) Which of the following is (are) proposed to be a function of telomeres? A. They are required for the complete replication of the chromosome. B. They form caps that protect the chromosomes from nucleases and other destabilizing influences. C. They prevent the ends of chromosomes from fusing with one another. D. All of these are correct answers.

D. All of these are correct answers.

Chromosomal aberrations include ________. A. Inversions B. Deletions C. Translocations D. All of these are correct answers.

D. All of these are correct answers.

Proteasomes are ________. A. Hollow and cylindrical B. Found in the nucleus and cytoplasm C. Involved in protein degradation D. All of these are correct answers.

D. All of these are correct answers.

Which cells below retain telomerase activity and thus have telomeres on their chromosomes that do not shrink? A. Germ cells B. Stem cells in the lining of the skin and the intestine C. The hematopoietic stem cells of the blood-forming tissues D. All of these are correct answers.

D. All of these are correct answers.

Which of the following properties of embryonic stem (ES) cells are present very early in development of a mammalian embryo? A. They are capable of differentiating into all of the different types of cells in the body. B. They are capable of indefinite self-renewal. C. They are pluripotent. D. All of these are correct answers.

D. All of these are correct answers.

Under what circumstances do cells express different genes? A. Cells at different stages of embryonic development express different genes. B. Cells in different tissues express different genes. C. Cells exposed to the same types of stimuli express different genes. D. Cells at different stages of embryonic development express different genes and cells in different tissues express different genes.

D. Cells at different stages of embryonic development express different genes and cells in different tissues express different genes.

Which of the nitrogenous bases in DNA is methylated in mammals and other vertebrates? A. Uracil B. Thymine C. Adenine D. Cytosine

D. Cytosine

Contrary to constitutive heterochromatin, facultative heterochromatin ______. A. Is permanently silenced B. Has been specifically inactivated during certain phases of an organism's life C. Is inactivated in certain types of differentiated cells D. Has been specifically inactivated during certain phases of an organism's life or is inactivated in certain types of differentiated cells

D. Has been specifically inactivated during certain phases of an organism's life or is inactivated in certain types of differentiated cells

What is chromatin that remains compacted during interphase called? This compacted, densely stained chromatin is found at the nuclear periphery. A. Granular chromatin B. Euchromatin C. Homochromatin D. Heterochromatin

D. Heterochromatin

Epigenetic inheritance involves _________________. A. Inheritance specified by DNA B. Inheritance specified by RNA C. Inherited characteristics that are not strictly dependent on RNA sequences D. Inherited characteristics that are not strictly dependent on DNA sequences

D. Inherited characteristics that are not strictly dependent on DNA sequences

A DNA-binding motif in which the amino acid leucine occurs every seventh amino acid along a stretch of α-helix is called _________. A. Zinc finger motif B. Helix-loop-helix (HLH) motif C. Leucine finger motif D. Leucine zipper motif

D. Leucine zipper motif

You are interpreting data on a DNA chip or microarray. You expose the chip to a mixture of two cDNA populations: one from cells that were not treated with a glucocorticoid hormone (untreated controls; labeled with a red fluorescent dye) and a population from cells that were treated with glucocorticoid hormones (glucocorticoid-treated; labeled with green fluorescent dye). You look at a spot on the chip representing the gene for esterase, a gene that is expressed in neither the untreated controls nor the glucocorticoid-treated cells. What color should the spot representing the esterase gene be? A. Red B. Green C. Yellow D. No color, the spot is not labeled

D. No color, the spot is not labeled

Which things below influence the particular transcript-processing pathway followed for a particular transcript in a cell? A. Particular stage of development being processed B. Particular cell type or tissue being processed C. Particular organelle being processed D. Particular stage of development being processed and particular cell type or tissue being processed

D. Particular stage of development being processed and particular cell type or tissue being processed

Since a DNA polymerase cannot synthesize DNA without a primer, some molecule other than DNA must be laid down as a primer to start replication. What molecule is laid down as a primer and which end of that molecule must be free and thus available to attach to new nucleotides? A. Protein, free 5' end B. RNA, free 5' end C. DNA, free 3' end D. RNA, free 3' end

D. RNA, free 3' end

Which of the following is not a general description of the gene expression regulation mechanisms that operate in eukaryotic organisms? A. Transcriptional-level controls B. Processing-level controls C. Translational-level controls D. Replication-level controls

D. Replication-level controls

What is thought to maintain X chromosome inactivation? A. Repressive histone modifications B. RNA inactivation C. DNA methylation D. Repressive histone modifications and DNA methylation

D. Repressive histone modifications and DNA methylation

With what is the space between the two membranes of the nuclear envelope continuous? A. The spindle B. The entire Golgi complex C. The chromosomes D. The ER lumen

D. The ER Lumen

If cells cannot replicate the ends of their DNA, what should happen with each round of cell division? A. The chromosomes should stay exactly the same length. B. The chromosomes should get longer. C. The mitotic spindle will shrink. D. The chromosomes should get shorter

D. The chromosomes should get shorter

Usually, alternatively spliced proteins are identical along most of their length, but they tend to differ in key regions that may affect certain properties of the proteins. What properties below are examples of those that are NOT likely to be altered by splicing? A. Cellular location B. Ligands they can bind C. Kinetics of catalytic activity D. The genetic code

D. The genetic code

With what structure is the outer membrane of the nuclear envelope continuous? A. RER B. SER C. Golgi complex D. The plasma membrane

D. The plasma membrane

What determines the repressor's ability to bind to the operator? A. The repressor's shape determines its ability to bind to the operator. B. Key metabolites affect the repressor's conformation allosterically. C. Key metabolites affect the repressor's conformation osmotically. D. The repressor's shape determines its ability to bind to the operator and key metabolites affect the repressor's conformation allosterically.

D. The repressor's shape determines its ability to bind to the operator and key metabolites affect the repressor's conformation allosterically.

If lactose is present in the medium in which bacteria are being cultured, which of the following statements is true? A. β-galactosidase is present at very few copies of the enzyme per cell. B. β-galactosidase mRNA is transcribed more than if lactose was not present. C. β-galactosidase is present at with many copies of the active enzyme per cell. D. β-galactosidase mRNA is transcribed more than if lactose was not present and β-galactosidase is present with many copies of the active enzyme per cell.

D. β-galactosidase mRNA is transcribed more than if lactose was not present and β-galactosidase is present with many copies of the active enzyme per cell.