Campbell Biology: chapter 18 Flashcards

1. What does the operon model attempt to explain? A) the coordinated control of gene expression in bacteria B) bacterial resistance to antibiotics C) how genes move between homologous regions of DNA D) the mechanism of viral attachment to a host cell E) horizontal transmission of plant viruses

1. The role of a metabolite that controls a repressible operon is to
   1. A) bind to the promoter region and decrease the affinity of RNA polymerase for the promoter.
   2. B) bind to the operator region and block the attachment of RNA polymerase to the promoter.
   3. C) increase the production of inactive repressor proteins.
   4. D) bind to the repressor protein and inactivate it.
   5. E) bind to the repressor protein and activate it.

1. The tryptophan operon is a repressible operon that is A) permanently turned on. B) turned on only when tryptophan is present in the growth medium. C) turned off only when glucose is present in the growth medium. D) turned on only when glucose is present in the growth medium. E) turned off whenever tryptophan is added to the growth medium.

1. This protein is produced by a regulatory gene: A) operon B) inducer C) promoter D) repressor E) corepressor

1. A mutation in this section of DNA could influence the binding of RNA polymerase to the DNA:
   1. A) operon B) inducer C) promoter D) repressor E) corepressor

1. A lack of this nonprotein molecule would result in the inability of the cell to ʺturn offʺ genes: A) operon B) inducer C) promoter D) repressor E) corepressor

1. When this is taken up by the cell, it binds to the repressor so that the repressor no longer binds to the operator: A) operon B) inducer C) promoter D) repressor E) corepressor

1. A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in A) continuous transcription of the structural gene controlled by that regulator. B) complete inhibition of transcription of the structural gene controlled by that regulator. C) irreversible binding of the repressor to the operator. D) inactivation of RNA polymerase by alteration of its active site. E) continuous translation of the mRNA because of alteration of its structure.

1. The lactose operon is likely to be transcribed when A) there is more glucose in the cell than lactose. B) the cyclic AMP levels are low. C) there is glucose but no lactose in the cell. D) the cyclic AMP and lactose levels are both high within the cell. E) the cAMP level is high and the lactose level is low.

1. Transcription of the structural genes in an inducible operon A) occurs continuously in the cell. B) starts when the pathwayʹs substrate is present. C) starts when the pathwayʹs product is present. D) stops when the pathwayʹs product is present. E) does not result in the production of enzymes.

1. How does active CAP induce expression of the genes of the lactose operon? A) It terminates production of repressor molecules. B) It degrades the substrate allolactose. C) It stimulates splicing of the encoded genes. D) It stimulates the binding of RNA polymerase to the promoter. E) It binds steroid hormones and controls translation.

1. For a repressible operon to be transcribed, which of the following must occur? A) A corepressor must be present. B) RNA polymerase and the active repressor must be present. C) RNA polymerase must bind to the promoter, and the repressor must be inactive. D) RNA polymerase cannot be present, and the repressor must be inactive. E) RNA polymerase must not occupy the promoter, and the repressor must be inactive.

1. Allolactose induces the synthesis of the enzyme lactase. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell? A) The repressor protein attaches to the regulator. B) Allolactose binds to the repressor protein. C) Allolactose binds to the regulator gene. D) The repressor protein and allolactose bind to RNA polymerase. E) RNA polymerase attaches to the regulator.

1. Altering patterns of gene expression in prokaryotes would most likely serve the organismʹs survival in which of the following ways? A) organizing gene expression so that genes are expressed in a given order B) allowing each gene to be expressed an equal number of times C) allowing the organism to adjust to changes in environmental conditions D) allowing young organisms to respond differently from more mature organisms E) allowing environmental changes to alter the prokaryoteʹs genome

1. in response to chemical signals, prokaryotes can do which of the following? A) turn off translation of their mRNA B) alter the level of production of various enzymes C) increase the number and responsiveness of their ribosomes D) inactivate their mRNA molecules E) alter the sequence of amino acids in certain proteins

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.

16) If she moves the promoter for the lac operon to the region between the beta galactosidase gene and the permease gene, which of the following would be likely?

A) Three structural genes will no longer be expressed. B) RNA polymerase will no longer transcribe permease.

C) The operon will no longer be inducible. D) Beta galactosidase will be produced.

E) The cell will continue to metabolize but more slowly.

1. If she moves the operator to the far end of the operon (past the transacetylase gene), which of the following would likely occur when the cell is exposed to lactose? A) The inducer will no longer bind to the repressor. B) The repressor will no longer bind to the operator. C) The operon will never be transcribed. D) The structural genes will be transcribed continuously. E) The repressor protein will no longer be produced.

1. 1. If she moves the repressor gene (lac I), along with its promoter, to a position at some several thousand base pairs away from its normal position, which will you expect to occur? A) The repressor will no longer be made. B) The repressor will no longer bind to the operator. C) The repressor will no longer bind to the inducer. D) The lac operon will be expressed continuously. E) The lac operon will function normally

1. If glucose is available in the environment of E. coli, the cell responds with very low concentration of cAMP. When the cAMP increases in concentration, it binds to CAP. Which of the following would you expect would then be a measurable effect? A) decreased concentration of the lac enzymes B) increased concentration of the trp enzymes C) decreased binding of the RNA polymerase to sugar metabolism-related promoters D) decreased concentration of alternative sugars in the cell E) increased concentrations of sugars such as arabinose in the cell

1. Muscle cells and nerve cells in one species of animal owe their differences in structure to A) having different genes. B) having different chromosomes. C) using different genetic codes. D) having different genes expressed. E) having unique ribosomes.

1. Which of the following mechanisms is (are) used to coordinately control the expression of multiple, related genes in eukaryotic cells?
   1. A) organization of the genes into clusters, with local chromatin structures influencing the expression of all the genes at once
   2. B) each of the genes sharing a common control element, allowing several activators to turn on their transcription, regardless of their location in the genome
   3. C) organizing the genes into large operons, allowing them to be transcribed as a single unit
   4. D) a single repressor able to turn off several related genes
   5. E) environmental signals that enter the cell and bind directly to their promoters

1. If you were to observe the activity of methylated DNA, you would expect it to A) be replicating nearly continuously. B) be unwinding in preparation for protein synthesis. C) have turned off or slowed down the process of transcription. D) be very actively transcribed and translated. E) induce protein synthesis by not allowing repressors to bind to it.

1. 23) Genomic imprinting, DNA methylation, and histone acetylation are all examples of A) genetic mutation. B) chromosomal rearrangements. C) karyotypes. D) epigenetic phenomena. E) translocation.

1. Approximately what proportion of the DNA in the human genome codes for proteins or functional RNA? A) 83% B) 46% C) 32% D) 13% E) 1.5%

1. Two potential devices that eukaryotic cells use to regulate transcription are A) DNA methylation and histone amplification. B) DNA amplification and histone methylation. C) DNA acetylation and methylation. D) DNA methylation and histone acetylation. E) histone amplification and DNA acetylation.

1. 26) In both eukaryotes and prokaryotes, gene expression is primarily regulated at the level of A) transcription. B) translation. C) mRNA stability. D) mRNA splicing. E) protein stability

1. In eukaryotes, transcription is generally associated with A) euchromatin only. B) heterochromatin only. C) very tightly packed DNA only. D) highly methylated DNA only. E) both euchromatin and histone acetylation.

1. The product of the bicoid gene in Drosophila could be considered a(n) A) tissue-specific protein. B) cytoplasmic determinant. C) maternal effect. D) inductive signal. E) fertilization product.

1. During DNA replication,
   1. A) all methylation of the DNA is lost at the first round of replication.
   2. B) DNA polymerase is blocked by methyl groups, and methylated regions of the genome are therefore left uncopied.
   3. C) methylation of the DNA is maintained because methylation enzymes act at DNA sites where one strand is already methylated and thus correctly methylates daughter strands after replication.
   4. D) methylation of the DNA is maintained because DNA polymerase directly incorporates methylated nucleotides into the new strand opposite any methylated nucleotides in the template.
   5. E) methylated DNA is copied in the cytoplasm, and unmethylated DNA in the nucleus.

1. Eukaryotic cells can control gene expression by which of the following mechanisms? A) histone acetylation of nucleosomes B) DNA acetylation C) RNA induced modification of chromatin structure D) repression of operons E) induction of operators in the promoter

1. In eukaryotes, general transcription factors A) are required for the expression of specific protein-encoding genes. B) bind to other proteins or to a sequence element within the promoter called the TATA box. C) inhibit RNA polymerase binding to the promoter and begin transcribing. D) usually lead to a high level of transcription even without additional specific transcription factors. E) bind to sequences just after the start site of transcription.

1. This binds to a site in the DNA far from the promoter to stimulate transcription: A) enhancer B) promoter C) activator D) repressor E) terminator

1. This can inhibit transcription by blocking the binding of positively acting transcription factors to the DNA: A) enhancer B) promoter C) activator D) repressor E) terminator

1. This is the site in the DNA located near the end of the final exon, encoding an RNA sequence that determines the 3ʹ end of the transcript: A) enhancer B) promoter C) activator D) repressor E) terminator

1. steroid hormones produce their effects in cells by A) activating key enzymes in metabolic pathways. B) activating translation of certain mRNAs. C) promoting the degradation of specific mRNAs. D) binding to intracellular receptors and promoting transcription of specific genes. E) promoting the formation of looped domains in certain regions of DNA.

1. A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see? A) increased chromatin condensation B) decreased chromatin concentration C) abnormalities of mouse embryos D) decreased binding of transcription factors E) inactivation of the selected genes

1. A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments she succeeded in decreasing methylation of histone tails. Which of the following results would she most likely see? A) increased chromatin condensation B) decreased chromatin concentration C) abnormalities of mouse embryos D) decreased binding of transcription factors E) inactivation of the selected genes

1. A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. One of her colleagues suggested she try increased methylation of C nucleotides in a mammalian system. Which of the following results would she most likely see? A) increased chromatin condensation B) decreased chromatin concentration C) abnormalities of mouse embryos D) decreased binding of transcription factors E) inactivation of the selected genes

1. A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. She tried decreasing the amount of methylation enzymes in the embryonic stem cells and then allowed the cells to further differentiate. Which of the following results would she most likely see? A) increased chromatin condensation B) decreased chromatin concentration C) abnormalities of mouse embryos D) decreased binding of transcription factors E) inactivation of the selected genes

1. Transcription factors in eukaryotes usually have DNA binding domains as well as other domains also specific for binding. In general, which of the following would you expect many of them to be able to bind? A) repressors B) ATP C) protein-based hormones D) other transcription factors E) tRNA

1. Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following?
   1. A) Eukaryotic mRNAs get 5ʹ caps and 3ʹ tails.
   2. B) Prokaryotic genes are expressed as mRNA, which is more stable in the cell.
   3. C) Eukaryotic exons may be spliced in alternative patterns.
   4. D) Prokaryotes use ribosomes of different structure and size.
   5. E) Eukaryotic coded polypeptides often require cleaving of signal sequences before localization.

1. Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell? A) enzymatic shortening of the poly(A) tail B) removal of the 5ʹ cap C) methylation of C nucleotides D) memethylation of histones E) removal of one or more exons

1. Which of the following is most likely to have a small protein called ubiquitin attached to it? A) a cyclin that usually acts in G1, now that the cell is in G2 B) a cell surface protein that requires transport from the ER C) an mRNA that is leaving the nucleus to be translated D) a regulatory protein that requires sugar residues to be attached E) an mRNA produced by an egg cell that will be retained until after fertilization

1. The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called A) RNA interference. B) RNA obstruction. C) RNA blocking. D) RNA targeting. E) RNA disposal.

1. At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. There was surprise expressed by many that the number of protein-coding sequences is much smaller than they had expected. Which of the following accounts for most of the rest?
   1. A) ʺjunkʺ DNA that serves no possible purpose
   2. B) rRNA and tRNA coding sequences
   3. C) DNA that is translated directly without being transcribed
   4. D) non-protein coding DNA that is transcribed into several kinds of small RNAs with biological function
   5. E) non-protein coding DNA that is transcribed into several kinds of small RNAs without biological function

1. Which of the following best describes siRNA?
   1. A) a short double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
   2. B) a single-stranded RNA that can, where it has internal complementary base pairs, fold into cloverleaf patterns
   3. C) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor
   4. D) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits
   5. E) a molecule, known as Dicer, that can degrade other mRNA sequences

1. One of the hopes for use of recent knowledge gained about non-coding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs?
   1. A) exploring a way to turn on the expression of pseudogenes
   2. B) targeting siRNAs to disable the expression of an allele associated with autosomal recessive disease
   3. C) targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease
   4. D) creating knock-out organisms that can be useful for pharmaceutical drug design
   5. E) looking for a way to prevent viral DNA from causing infection in humans

1. Which of the following describes the function of an enzyme known as Dicer? A) It degrades single-stranded DNA. B) It degrades single-stranded mRNA. C) It degrades mRNA with no poly(A) tail. D) It trims small double-stranded RNAs into molecules that can block translation. E) It chops up single-stranded DNAs from infecting viruses.

1. In a series of experiments, the enzyme Dicer has been inactivated in cells from various vertebrates, and the centromere is abnormally formed from chromatin. Which of the following is most likely to occur?
   1. A) The usual mRNAs transcribed from centromeric DNA will be missing from the cells.
   2. B) Tetrads will no longer be able to form during meiosis I.
   3. C) Centromeres will be euchromatic rather than heterochromatic and the cells will soon die in culture.
   4. D) The cells will no longer be able to resist bacterial contamination.
   5. E) The DNA of the centromeres will no longer be able to replicate.

1. Since Watson and Crick described DNA in 1953, which of the following might best explain why the function of small RNAs is still being explained?
   1. A) As RNAs have evolved since that time, they have taken on new functions.
   2. B) Watson and Crick described DNA but did not predict any function for RNA.
   3. C) The functions of small RNAs could not be approached until the entire human genome was sequenced.
   4. D) Ethical considerations prevented scientists from exploring this material until recently.
   5. E) Changes in technology as well as our ability to determine how much of the DNA is expressed have now made this possible.

A researcher has arrived at a method to prevent gene expression from Drosophila embryonic genes. The following questions assume that he is using this method.

51) The researcher in question measures the amount of new polypeptide production in embryos from 2—8 hours following fertilization and the results show a steady and significant rise in polypeptide concentration over that time. The researcher concludes that

1. A) his measurement skills must be faulty.
2. B) the results are due to building new cell membranes to compartmentalize dividing nuclei.
3. C) the resulting new polypeptides are due to translation of maternal mRNAs.
4. D) the new polypeptides were inactive and not measurable until fertilization.
5. E) polypeptides were attached to egg membranes until this time.

1. The researcher continues to study the reactions of the embryo to these new proteins and you hypothesize that he is most likely to see which of the following (while embryonic genes are still not being expressed)? A) The cells begin to differentiate. B) The proteins are evenly distributed throughout the embryo. C) Larval features begin to make their appearance. D) Spatial axes (anterior → posterior, etc.) begin to be determined. E) The embryo begins to lose cells due to apoptosis from no further gene expression.

1. he researcher measures the concentration of the polypeptides from different regions in the early embryo and finds the following pattern (darker shading = greater concentration): Which of the following would be his most logical assumption?
   1. A) The substance has moved quickly from region 5 to region 1.
   2. B) Some other material in the embryo is causing accumulation in region 1 due to differential binding.
   3. C) The cytosol is in constant movement, dispersing the polypeptide.
   4. D) The substance is produced in region 1 and diffuses toward region 5.
   5. E) The substance must have entered the embryo from the environment near region 1.

1. You are given an experimental problem involving control of a geneʹs expression in the embryo of a particular species. One of your first questions is whether the geneʹs expression is controlled at the level of transcription or translation. Which of the following might best give you an answer?
   1. A) You explore whether there has been alternative splicing by examining amino acid sequences of very similar proteins.
   2. B) You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.
   3. C) You assess the position and sequence of the promoter and enhancer for this gene.
   4. D) An analysis of amino acid production by the cell shows you that there is an increase at this stage of embryonic life.
   5. E) You use an antibiotic known to prevent translation.

1. In humans, the embryonic and fetal forms of hemoglobin have a higher affinity for oxygen than that of adults. This is due to
   1. A) nonidentical genes that produce different versions of globins during development.
   2. B) identical genes that generate many copies of the ribosomes needed for fetal globin production.
   3. C) pseudogenes, which interfere with gene expression in adults.
   4. D) the attachment of methyl groups to cytosine following birth, which changes the type of hemoglobin produced.
   5. E) histone proteins changing shape during embryonic development.

1. The process of cellular differentiation is a direct result of A) differential gene expression. B) morphogenesis. C) cell division. D) apoptosis. E) differences in cellular genomes.

1. The fact that plants can be cloned from somatic cells demonstrates that A) differentiated cells retain all the genes of the zygote. B) genes are lost during differentiation. C) the differentiated state is normally very unstable. D) differentiated cells contain masked mRNA. E) differentiation does not occur in plants

1. A cell that remains entirely flexible in its developmental possibilities is said to be A) differentiated. B) determined. C) totipotent. D) genomically equivalent. E) epigenetic.

1. Differentiation of cells is not easily reversible because it involves
   1. A) changes in the nucleotide sequence of genes within the genome.
   2. B) changes in chromatin structure that make certain regions of the genome more accessible.
   3. C) chemical modifications of histones and DNA methylation.
   4. D) frameshift mutations and inversions.
   5. E) excision of some coding sequences.

1. In animals, embryonic stem cells differ from adult stem cells in that
   1. A) embryonic stem cells are totipotent, and adult stem cells are pluripotent.
   2. B) embryonic stem cells are pluripotent, and adult stem cells are totipotent.
   3. C) embryonic stem cells have more genes than adult stem cells.
   4. D) embryonic stem cells have fewer genes than adult stem cells.
   5. E) embryonic stem cells are localized to specific sites within the embryo, whereas adult stem cells are spread throughout the body.

1. Which of the following statements is true about stem cells? A) Stem cells can continually reproduce and are not subject to mitotic control. B) Stem cells can differentiate into specialized cells. C) Stem cells are found only in bone marrow. D) Stem cells are found only in the adult human brain. E) Stem cell DNA lacks introns.

1. What is considered to be the first evidence of differentiation in the cells of an embryo? A) cell division B) the occurrence of mRNAs for the production of tissue-specific proteins C) determination D) changes in the size and shape of the cell E) changes resulting from induction

1. In most cases, differentiation is controlled at which level? A) replication of the DNA B) nucleosome formation C) transcription D) translation E) post-translational activation of the proteins

1. Which of the following serve as sources of developmental information? A) cytoplasmic determinants such as mRNAs and proteins produced before fertilization B) signal molecules produced by the maturing zygote C) ubiquitous enzymes such as DNA polymerase and DNA ligase D) paternally deposited proteins E) specific operons within the zygote genome

1. The MyoD protein
   1. A) can promote muscle development in all cell types.
   2. B) is a transcription factor that binds to and activates the transcription of muscle-related genes.
   3. C) was used by researchers to convert differentiated muscle cells into liver cells.
   4. D) magnifies the effects of other muscle proteins.
   5. E) is a target for other proteins that bind to it.

1. The gene for which protein would most likely be expressed as a result of MyoD activity? A) myosin B) crystallin C) albumin D) hemoglobin E) DNA polymerase

1. The general process that leads to the differentiation of cells is called A) determination. B) specialization. C) identification. D) differentialization. E) cellularization.

1. Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development? A) morphogenesis B) determination C) induction D) differentiation E) pattern formation

1. Which of the following is established prior to fertilization in Drosophila eggs? A) the anterior-posterior and dorsal-ventral axes B) the position of the future segments C) the position of the future wings, legs, and antennae D) A and B only E) A, B, and C

1. The product of the bicoid gene in Drosophila provides essential information about A) the anterior-posterior axis. B) the dorsal-ventral axis. C) the left-right axis. D) segmentation. E) lethal genes.

1. If a Drosophila female has a homozygous mutation for a maternal effect gene,
   1. A) she will not develop past the early embryonic stage.
   2. B) all of her offspring will show the mutant phenotype, regardless of their genotype.
   3. C) only her male offspring will show the mutant phenotype.
   4. D) her offspring will show the mutant phenotype only if they are also homozygous for the mutation.
   5. E) only her female offspring will show the mutant phenotype.

1. Mutations in these genes lead to transformations in the identity of entire body parts: A) homeotic genes B) segmentation genes C) egg-polarity genes D) morphogens E) inducers

1. These genes are expressed by the mother, and their products are deposited into the developing egg: A) homeotic genes B) segmentation genes C) egg-polarity genes D) morphogens E) inducers

1. These genes map out the basic subdivisions along the anterior-posterior axis of the Drosophila embryo: A) homeotic genes B) segmentation genes C) egg-polarity genes D) morphogens E) inducers

1. These genes form gradients and help establish the axes and other features of an embryo: A) homeotic genes B) segmentation genes C) egg-polarity genes D) morphogens E) inducers

1. Gap genes and pair-rule genes fall into this category: A) homeotic genes B) segmentation genes C) egg-polarity genes D) morphogens E) inducers

1. The product of the bicoid gene in Drosophila could be considered a(n) A) tissue-specific protein. B) cytoplasmic determinant. C) maternal effect. D) inductive signal. E) fertilization product.

1. The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur? A) The embryo would grow to an unusually large size. B) The embryo would grow extra wings and legs. C) The embryo would probably show no anterior development and die. D) Anterior structures would form in both sides of the embryo. E) The embryo would develop normally.

1. What do gap genes, pair-rule genes, segment polarity genes, and homeotic genes all have in common? A) Their products act as transcription factors. B) They have no counterparts in animals other than Drosophila. C) Their products are all synthesized prior to fertilization. D) They act independently of other positional information. E) They apparently can be activated and inactivated at any time of the flyʹs life.

1. Which of the following statements describes proto-oncogenes? A) They can code for proteins associated with cell growth. B) They are introduced to a cell initially by retroviruses. C) They are produced by somatic mutations induced by carcinogenic substances. D) Their normal function is to suppress tumor growth E) They are underexpressed in cancer cells

1. Which of the following is characteristic of the product of the p53 gene?
   1. A) It is an activator for other genes.
   2. B) It speeds up the cell cycle.
   3. C) It causes cell death via apoptosis.
   4. D) It allows cells to pass on mutations due to DNA damage.
   5. E) It slows down the rate of DNA replication by interfering with the binding of DNA polymerase.

1. Tumor suppressor genes A) are frequently overexpressed in cancerous cells. B) are cancer-causing genes introduced into cells by viruses. C) can encode proteins that promote DNA repair or cell-cell adhesion. D) often encode proteins that stimulate the cell cycle. E) all of the above

1. The incidence of cancer increases dramatically in older humans because A) the Ras protein is more likely to be hyperactive after age sixty. B) proteasomes become more active with age. C) as we age, normal cell division inhibitors cease to function. D) the longer we live, the more mutations we accumulate. E) tumor-suppressor genes are no longer able to repair damaged DNA.

1. The cancer-causing forms of the Ras protein are involved in which of the following processes? A) relaying a signal from a growth factor receptor B) DNA replication C) DNA repair D) cell-cell adhesion E) cell division

1. Forms of the ras protein found in tumors usually cause which of the following? A) DNA replication to stop B) DNA replication to be hyperactive C) cell-to-cell adhesion to be nonfunctional D) cell division to cease E) growth factor signaling to be hyperactive

1. A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type(s) of cancer? A) colorectal only B) lung and breast C) small intestinal and esophageal D) lung only E) lung and prostate

1. Which of the following can contribute to the development of cancer? A) random spontaneous mutations B) mutations caused by X-rays C) transposition D) chromosome translocations E) all of the above

1. One hereditary disease in humans, called xeroderma pigmentosum (XP), makes homozygous individuals exceptionally susceptible to UV-induced mutation damage in the cells of exposed tissue, especially skin. Without extraordinary avoidance of sunlight exposure, patients soon succumb to numerous skin cancers. Which of the following best describes this phenomenon? A) inherited cancer taking a few years to be expressed B) embryonic or fetal cancer C) inherited predisposition to mutation D) inherited inability to repair UV-induced mutation E) susceptibility to chemical carcinogens

A few decades ago, Knudsen and colleagues proposed a theory that, for a normal cell to become a cancer cell, a minimum of two genetic changes had to occur in that cell. Knudsen was studying retinoblastoma, a childhood cancer of the eye.

1. 89) If there are two children born from the same parents, and child one inherits a predisposition to retinoblastoma (one of the mutations) and child two does not, but both children develop the retinoblastoma, which of the following would you expect? A) an earlier age of onset in child one B) a history of exposure to mutagens in child one but not in child two C) a more severe cancer in child one D) increased levels of apoptosis in both children E) decreased levels of DNA repair in child one

1. In colorectal cancer, several genes must be mutated in order to make a cell a cancer cell, supporting Knudsenʹs hypothesis. Which of the following kinds of genes would you expect to be mutated? A) genes coding for enzymes that act in the colon B) genes involved in control of the cell cycle C) genes that are especially susceptible to mutation D) the same genes that Knudsen identified as associated with retinoblastoma E) the genes of the bacteria that are abundant in the colon

1. One of the human leukemias, called CML (chronic myelogenous leukemia) is associated with a chromosomal translocation between chromosomes 9 and 22 in somatic cells of bone marrow. Which of the following allows CML to provide further evidence of this multi-step nature of cancer?
   1. A) CML usually occurs in more elderly persons (late age of onset).
   2. B) The resulting chromosome 22 is abnormally short; it is then known as the Philadelphia chromosome.
   3. C) The translocation requires breaks in both chromosomes 9 and 22, followed by fusion between the reciprocal pieces.
   4. D) CML involves a proto-oncogene known as abl.
   5. E) CML can usually be treated by chemotherapy.

1. if a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then the A) amino acid inactivates the repressor. B) enzymes produced are called inducible enzymes. C) repressor is active in the absence of the amino acid. D) amino acid acts as a corepressor. E) amino acid turns on transcription of the operon.

1. Muscle cells differ from nerve cells mainly because they A) express different genes. B) contain different genes. C) use different genetic codes. D) have unique ribosomes. E) have different chromosomes.

1. What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? A) irreversible binding of the repressor to the promoter B) reduced transcription of the operonʹs genes C) buildup of a substrate for the pathway controlled by the operon D) continuous transcription of the operonʹs genes E) overproduction of catabolite activator protein (CAP)

1. The functioning of enhancers is an example of A) transcriptional control of gene expression. B) a post-transcriptional mechanism for editing mRNA. C) the stimulation of translation by initiation factors. D) post-translational control that activates certain proteins. E) a eukaryotic equivalent of prokaryotic promoter functioning.

1. Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene A) is transcribed in the early embryo. B) normally leads to formation of tail structures. C) normally leads to formation of head structures. D) is a protein present in all head structures. E) leads to programmed cell death.

1. Which of the following statements about the DNA in one of your brain cells is true? A) Most of the DNA codes for protein. B) The majority of genes are likely to be transcribed. C) Each gene lies immediately adjacent to an enhancer. D) Many genes are grouped into operon-like clusters. E) It is the same as the DNA in one of your heart cells.

1. Cell differentiation always involves the A) production of tissue-specific proteins, such as muscle actin. B) movement of cells. C) transcription of the myoD gene. D) selective loss of certain genes from the genome. E) cellʹs sensitivity to environmental cues such as light or heat.

1. Which of the following is an example of post-transcriptional control of gene expression? A) the addition of methyl groups to cytosine bases of DNA B) the binding of transcription factors to a promoter C) the removal of introns and splicing together of exons D) gene amplification during a stage in development E) the folding of DNA to form heterochromatin

1. Within a cell, the amount of protein made using a given mRNA molecule depends partly on A) the degree of DNA methylation. B) the rate at which the mRNA is degraded. C) the presence of certain transcription factors. D) the number of introns present in the mRNA. E) the types of ribosomes present in the cytoplasm.

1. Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells? A) Proto-oncogenes first arose from viral infections. B) Proto-oncogenes normally help regulate cell division. C) Proto-oncogenes are genetic ʺjunk.ʺ D) Proto-oncogenes are mutant versions of normal genes. E) Cells produce proto-oncogenes as they age.