Which of the following structures is not part of an operon?
A. regulator gene
B. promoter
C. operator
D. structural gene
E. all of these are part of an operon
E
When a bacterium is introduced to a new environment that is an appropriate medium for that species to grow, fission allows a rapid expansion of the population (2-4-8-16-32-64 . . . etc.). But there is usually a slight lag before the bacteria actually begin building up such a logarithmic growth curve. What is the best explanation?
A. It takes time for sub-cellular units to evolve the ability to digest new media.
B. A bacterium is not actively producing all the enzymes it can code for, and it takes time to induce and amplify the production of the currently needed enzymes.
C. Binary fission becomes more and more efficient.
D. A new media dissolves away repressor proteins.
E. Structural genes act more slowly than metabolic genes.
B
In the lac operon, if lactose is present, which of the following occurs?
A. Lactose binds to the repressor, changing its shape so that it can bind to the operator and the structural genes are not expressed.
B. Lactose bind to RNA polymerase, which then binds to the promoter and transcribes the needed genes.
C. Lactose binds to the repressor, changing its shape so that it does not bind to the operator. RNA polymerase then transcribes the needed genes.
D. Lactose binds to the operon, which attracts RNA polymerase, then transcription of the needed genes occurs.
C
Active genes in eukaryotic cells are associated with
A. euchromatin.
B. heterochromatin.
C. methylated RNA and histones.
D. DNA with many methyl groups.
A
The term "operon" comes from the Latin root word for
A. gene.
B. structure.
C. controller.
D. work.
E. copy-producing.
D.
Which component in an operon is incorrectly matched with its function?
A. promoter—where RNA polymerase first binds to DNA
B. regulator gene—binds to the repressor protein
C. structural gene—makes mRNA by transcription
D. operator—if not bound to repressor, allows RNA polymerase to bind to DNA
B
Which statement is NOT correct about the lac operon?
A. It regulates the production of a series of five enzymes.
B. It is normally turned off if glucose is present.
C. Lactose binds to the repressor protein and inactivates it.
D. It is an inducible system.
E. The structural genes make products that allow lactose metabolism.
A
Which statement is NOT correct about the trp operon?
A. The structural genes make products that are part of an anabolic pathway for the synthesis of tryptophan.
B. It is normally turned off if tryptophan is present.
C. Tryptophan acts as the corepressor.
D. The regulator gene product is inactive by itself.
E. Tryptophan binds to the repressor protein and inactivates it.
E
What is the proper sequence those events that take place in the lac operon as lactose is introduced to a bacterial culture?
1. RNA polymerase binds to a promoter on the DNA to begin RNA synthesis.
2. The structural genes are transcribed.
3. A regulator gene normally codes for a repressor that binds to the operator and prevents transcription.
4. Lactose binds to the repressor and prevents it from binding to the operator.
A. 4,3,2,1
B. 4,3,2,1
C. 3,4,1,2
D. 2,3,4,2
A
The universal regulatory mechanism in eukaryotes for controlling gene expression includes
A. control of the genes transcribed and the rate they are transcribed.
B. control of the processing of mRNA after it is transcribed from DNA but before it leaves the nucleus, and control of the rate it leaves the nucleus.
C. control of mRNA in the cytoplasm after it leaves the nucleus, including changes to mRNA before translation begins.
D. control of polypeptides after they have been synthesized but before they are functional.
E. All of these mechanisms are used; there is no single universal mechanism.
E
_______ control is the most critical level of eukaryotic genetic control.
A. Feedback
B. Translational
C. Transcriptional
D. Posttranscriptional
E. Posttranslational
C
_________ control is the level of genetic control that involves the life span of the mRNA molecule and the ability of the mRNA to bind to ribosomes.
A. Feedback control
B. Translational control
C. Transcriptional control
D. Posttranscriptional control
E. Posttranslational control
B
_________ is the level of genetic control that involves the processing of early RNA transcripts to mRNA and the rate at which mRNA leaves the nucleus.
A. Feedback control
B. Translational control
C. Transcriptional control
D. Posttranscriptional control
E. Posttranslational control
D
Which level of primary control in eukaryotic gene activity involves changes in the polypeptide chain before it becomes functional?
A. feedback control
B. translational control
C. transcriptional control
D. posttranscriptional control
E. posttranslational control
E
In transcriptional control in eukaryotic cells
A. a different combination of DNA binding proteins (transcriptional factors) may regulate the activity of a particular gene.
B. enhancers may be involved in the promotion as well as regulation of gene transcription.
C. the control may be due to the phosphorylation of transcriptional factors by a kinase.
D. All of the choices are correct.
E. Only two of the choices are correct.
D
The mRNA strand includes both introns and exons.
FALSE
A form of gene regulation that occurs while RNA is still in the nucleus is
A. differential intron removal and splicing.
B. feedback control.
C. enzymatic cleavage of a polypeptide.
D. rate of binding to ribosomes.
A
Human red blood cells can live from two to four months without a nucleus and yet they continue to synthesize hemoglobin. This
A. means that the necessary mRNAs are able to persist all this time.
B. suggests that there is a low level of ribonucleases to degrade the mRNA.
C. is a chemical process that does not require continued living pathways. The red blood cells are essentially dead after they lose their nuclei.
D. All of the choices are true.
E. Only two of the choices are correct.
E
"Jumping genes" that have the ability to move within and between chromosomes are called
A. introns.
B. oncogenes.
C. transposons.
D. retroviruses.
E. exons.
C
A deletion of one base pair that alters the sequence of codons is called a(n)
A. transposon.
B. substitution mutation.
C. carcinogen.
D. oncogene.
E. frameshift mutation.
E
Which of the following is a method of posttranscriptional control?
A. transcription factors
B. the life span of a mRNA molecule
C. differential processing of mRNA
D. how fast the mRNA leaves the nucleus
E. Both C and D are methods of posttranscriptional control.
E
Mutagens and carcinogens are associated with
A. induced mutations.
B. spontaneous mutations.
C. transposon activity.
D. DNA replication errors.
A
All of these are considered carcinogens EXCEPT
A. cigarette smoke.
B. ultraviolet light.
C. cabbage and related vegetables.
D. acrylamide, a natural product found in French fries.
E. mold produced aflatoxin.
C
An oncogene is
A. a viral gene with no relation to the host cell's genes.
B. a mutated form of a proto-oncogene.
C. a bacterial gene that causes cancer in the host.
D. always seen in human cancer cells.
E. a gene that turns off cellular reproduction.
B
You are more likely to develop some forms of cancer if you
A. are exposed to higher doses of radiation including X rays.
B. are exposed to carcinogens.
C. have a high incidence of cancer in your family history.
D. All of the choices are correct.
D
The DNA of a _______ is wrapped around histone molecules to form a "beaded string."
A. prokaryote
B. eukaryote
C. bacterium
D. All of the above.
B
Identify the major tumor suppressor gene that is more frequently mutated in human cancers than any other known gene.
A. p53 gene
B. hemoglobin gene
C. ras oncogene
D. p16
E. RB tumor-repressor gene
A
Thymine dimers
A. form when DNA is exposed to carcinogens such as tobacco smoke.
B. are rarely removed by DNA repair enzymes.
C. form when DNA is exposed to UV radiation.
D. result in abnormal protein structure which causes red blood cells to sickle.
C
Transposons
A. are specific DNA sequences that move within and between chromosomes.
B. alter the expression of neighboring genes especially if the transposon is a regulator gene.
C. have been discovered in corn, fruit flies, bacteria, and humans.
D. All of the choices are correct.
D
Point mutations
A. are due to a change in one DNA nucleotide.
B. may change a specific codon.
C. can cause a genetic disease such as sickle cell disease that is due to a base change that codes for valine rather than glutamate.
D. All of the choices are correct.
D
Frameshift mutations
A. most often happen when one or more nucleotides are inserted or deleted from the DNA.
B. can result in a completely new codon sequence that results in the production of non-functional proteins.
C. applies to the reading frame (sequence of codons) being changed.
D. All of the choices are correct.
D
Androgen insensitivity is characterized by
A. a lack of male hormones, such as testosterone.
B. external female genitalia.
C. a female karyotype.
D. the internal sex organs of a female and may bear children.
B
A change in a regulatory gene
A. must be dominant to be effective.
B. is what happens in the production of sickle cell hemoglobin.
C. is always beneficial to the organism in which it occurs.
D. can increase or decrease the expression of a structural gene.
D
A Barr body
A. is only found in male cells.
B. is an inactive Y chromosome that produces reduced amount of gene products.
C. is an inactive X chromosome that does not produce gene products.
D. All of the choices are correct.
C
If a chromosome is highly methylated,
A. the gene is expressed, producing more gene product than normal.
B. the gene is not expressed, even if it is a normal gene in every other way.
C. the gene is expressed, but reduced quantities protein are made.
D. there is no affect on gene expression.
B
Xeroderma pigmentosum
A. is characterized by a deficiency of RNA repair enzymes.
B. is characterized by lung and colon cancers.
C. leaves the liver cells vulnerable to the mutagenic effects of UV light.
D. is associated with a high incidence of skin cancer.
D
____________ occurs as ____________ builds up in the system if Enzyme A is nonfunctional because of an inherited mutation.
A. albinism; melanin
B. xeroderma pigmentosum; tyrosine
C. phenylketonuria; phenyalanine
D. androgen insensitivity; tyrosine
C
Germ-line mutations
A. occur in sex cells.
B. can be passed to subsequent generations.
C. may range from having no effect to completely inactivating protein activity.
D. All of the above are true about germ line mutations.
E. Only two of the above are true.
D
The regulator gene codes for the DNA-binding proteins that act as repressors.
TRUE
All genes are active at the same time in a prokaryotic cell and controlled by positive regulation, but not in a eukaryotic cell.
FALSE
Once proteins are made and functional, they are no longer subject to cellular control.
FALSE
The genes of a single operon are all regulated by the same repressor, operator, and promoter.
TRUE
In the transcription of DNA, remodeling proteins push the histone portion of the nucleosome aside so that transcription may begin.
TRUE
One third of all cancer deaths are due to mutations that arise from smoking tobacco.
TRUE
Which of the following situations would be considered an example of positive regulation of gene expression in a prokaryote?
A. The CAP protein regulating the lac operon to be active when glucose is absent and lactose is present.
B. The CAP protein regulating the lac operon to be active when lactose is absent and glucose is present.
C. The repressor protein regulating the lac operon to be active when glucose is absent and lactose is present.
D. The repressor protein regulating the lac operon to be active when lactose is absent and glucose is present.
A
If CAP is absent from a cell what are the potential consequences?
A. The individual cannot activate the catabolism of various other metabolites in the absence of glucose.
B. The individual does not have a backup system for survival when glucose is absent.
C. The individual will most likely die because they cannot metabolize enough energy if glucose is absent.
D. All of these are consequences of the absence of CAP.
D
Which of the following problems can arise during posttransriptional control?
A. Differential splicing of exons that can lead to an altered gene expression.
B. Not excising all of introns from the pre-mRNA strand, leaving fragments to be joined with the exons.
C. Excising an exon from the pre-mRNA strand.
D. All of these are errors that can occur during posttranscriptional control of gene expression.
D
Which of the following series of events is associated with the formation of cancer?
A. The proto-oncogenes mutate and become oncogenes which are continuously active. There is also an associated loss of tumor suppressor gene activity allowing uncontrolled growth of cells.
B. The oncogenes mutate and become proto-oncogenes which are continuously active. There is also an associated loss of tumor suppressor gene activity allowing uncontrolled growth of cells.
C. The proto-oncogenes mutate and become oncogenes which stop functioning altogether. There is also an associated increase in the tumor suppressor gene activity allowing uncontrolled growth of cells.
D. The oncogenes mutate and become proto-oncogenes which stop functioning altogether. There is also an associated increase in the tumor suppressor gene activity allowing uncontrolled growth of cells.
A
What complications could arise if an individual had a genetic disorder that prevented them from forming 25% of their histones?
A. The chromatin would not condense properly and some of it would not be available for transcriptional machinery resulting in the expression of additional genes.
B. The chromatin would not condense properly and some of it would not be available for transcriptional machinery resulting in the decreased expression of their genes.
C. The chromatin would condense more than normal and result in the expression of additional genes.
D. The chromatin would condense more than normal and result in the expression of fewer than normal genes.
A