A gene encoding growth hormone in rats was introduced into mice. The construct used consisted in an open reading frame encoding rat growth hormone fused to a mouse promoter A. The growth hormone sequence was obtained from a rat cDNA library, the only available source of sequence information. Fertilized mouse egg cells were transformed with the rat growth hormone construct and expression of the rat growth hormone was detected. Transformation of fertilized egg cells with rat growth hormone cDNA alone did not result in expression.
1. Why was it necessary to fuse the rat growth hormone sequence to a promoter to obtain expression?
A. The rat sequence was obtained from a cDNA library and therefore did not include a promoter sequence.
B. No factors that recognized the rat promoter sequence were present in the mouse.
C. The rat promoter was contained within the rat sequence but was inactivated in the mouse.
D. Rat growth hormone is inactive in mice.
2. When the eggs were placed under conditions conducive to activation of the mouse promoter, one of the resulting offspring grew larger than the expected size. The appearance of the large mouse is consistent with one of the following statements:
A. That mouse grew bigger because it produced more mouse growth hormone.
B. That mouse grew bigger because it was more aggressive and ate more mouse chow.
C. That mouse grew bigger because the mouse promoter A was activated, resulting in increased production of rat growth hormone.
D. That mouse grew bigger because his nose was longer.
3. The mouse promoter used is controlled by zinc. It controls the expression of metallothionein, a zinc-binding protein that regulates the level of that metal in mouse cells. It is important to control intracellular zinc levels because
A. Zinc is toxic at all levels.
B. Intracellular levels of zinc must be kept within certain narrow limits to avoid toxic responses.
C. Although zinc is not required for the regulation of transcription, it is required for translational control.
D. None of the above.
The researchers now want to get information about the corresponding gene in mice. They have identified a strain of true-breeding mice that do not grow to full size (dwarfism). Their thought is that if they could understand this sluggish growth in mice, that perhaps they could begin to understand dwarfism in humans. The research team sets out to isolate and clone the growth hormone gene in mice, starting from the rat gene. They have a mouse cDNA library available to them.
4. The first step in their new project involves:
A. Screening a mouse genomic library.
B. Probing the mouse cDNA library with cDNA encoding the rat growth hormone.
C. Probing a rat genomic library with mouse cDNA encoding mouse growth hormone.
D. Amplifying mouse cDNAs encoding growth hormone.
5. The team has now succeeded in identifying a candidate for the open reading frame encoding the mouse growth hormone. The final step in the procedure, which resulted in a tentative identification of the sequence as a growth hormone gene involved:
A. Purifying the candidate sequence on an agarose gel.
B. Sequencing the DNA.
C. Using the sequence, once known, to scan GenBank to identify homologous cDNA sequences.
D. Using the primary sequence, once known, to infer the definitive 3-D molecular structure of the protein.
6. Armed with the mouse growth hormone cDNA, the researchers now want to get more information about regulation of the mouse growth hormone gene. Their first step will be to:
A. Identify and clone the mouse growth hormone genomic sequence.
B. Search for transcription factors that bind to the known promoter sequence of the mouse growth hormone gene.
C. Search for transcription factors that bind to the known promoter sequence of the rat growth hormone gene.
D. Search for the promoter sequence of the rat growth hormone gene.
7. They now propose to use the dwarf mice to get more information concerning mouse growth hormone function. A first measurement shows that growth hormone levels and body weight in dwarf mice are the same at birth as in normal size mice but that levels do not increase at the same rate in the former as they do in the latter (50 separate matings in each case). This could be due to:
A. Lack of responsiveness in the dwarf mice pups of the growth hormone promoter to activating factors produced during development.
B. Accidental environmental factors affecting the dwarf mouse mothers.
C. Accidental environmental factors affecting the dwarf mouse fathers.
D. None of the above.
Much attention is currently focused on the potential long-term environmental dangers of producing transgenic organisms. In many countries in Western Europe consumer action has resulted in the specific labeling of food obtained from genetically engineered crop plants. Initially, scientists were unmoved by this groundswell of public opinion. Now the tide is beginning to turn, and potential risks are being assessed or at least discussed by the biotechnology community.
8. An introduced gene could:
A. Cause silencing of endogenous genes.
B. Not cause high levels of a toxic compound to accumulate.
C. Not cause any alteration in endogenous gene expression or regulation.
D. Cause mutations to occur with increased frequency in the host plant.
9. Selection markers are commonly used to identify transgenic organisms in the initial stages of their production. These markers are thought to pose a potential risk if they are allowed to remain in transgenic crop plants when they are released for agricultural use. Selection markers could:
A. Silence endogenous gene expression.
B. Stimulate cancerous growth.
C. Impart antibiotic resistance.
D. Do no foreseeable harm.
10. The next generation of genetically modified crops may include "functional foods" such as plants with increased vitamin levels. Safety trials will be implemented for these super-vitamin producers. Plants that produce increased amounts of a particular vitamin:
A. will produce less other essential vitamins.
B. will have reduced rates of photosynthetic carbon fixation.
C. may produce the vitamin at a toxic level since production rates within the plant cannot yet be controlled.
D. will not pose any substantial risk to consumers.
Your doctor, a researcher in medical genetics, tells you that you have a rare genetic condition, which is controlled by one gene alone, in which a protein present in your brain cells makes you think faster than your biological brother. You want to get more information about your great intellectual advantage. The doctor has two samples of DNA, one a copy of the gene from your body and the other from your brother's. She tells you that each sample encodes one form of the brain protein in question. The DNA sequences have not been made public yet, and the doctor is sure that her discovery will make her famous, so she is unwilling to give you access to the DNA samples. A friendly technician in the doctor's group, however, carries out in vitro transcription and translation of these two DNA samples and slips you some of each of the two translation products.
11. What method could you use to get information about these translation products?
A. Nucleotide sequencing
C. N-terminal amino acid sequencing
D. RNase protection assays
12. The process by which you can use information gleaned from examination of the translation products to learn about the two DNA sequences is called:
A. Reverse genetics
B. Database mining
C. Computational biology
D. Classical genetics
13. Which molecular property of the brain protein might differ between you and your brother if the protein in question were an enzyme?
A. Lariat structure
B. Differences in sequence of active sites
C. The presence of thymine-thymine dimers
D. RNase activity
14. What difference might you find in the samples if the brain protein were a membrane receptor?
A. Proteolytic activity of more efficient protein would be higher than the other form
B. Proteolytic activity of the less efficient protein would be higher than the other form
C. Differences in binding properties for signaling molecule
D. Participation in DNA repair
15. What difference between your brain protein gene and that of your brother would explain the observed difference between the 2 proteins?
A. Altered promoter activities
B. Stability of transcripts
C. Differences in 3'-untranslated sequences
D. Differences in open reading frame
16. The first step in analysis of the two samples of brain proteins leads directly to:
A. A partial knowledge of the sequence of the open reading frames
B. A knowledge of the genomic sequences
C. A knowledge of site of binding of transcription factors
D. An understanding of the functional differences between the 2 proteins
Your brother is about to start a family. You decide that this advantage of yours should be shared by your brother's children. You ask your doctor about the possibility of carrying out gene therapy to ensure that each of the children born to your brother and his wife have the more efficient brain protein gene. The doctor immediately refuses for a non-scientific reason.
17. She does so because:
A. The procedure might fail.
B. The procedure might damage the developing embryo.
C. The procedure is illegal germline therapy and she would lose her US license.
D. The procedure would cost a lot of money.
18. Objections have been raised against using the potential power of biotechnology to fight genetically-based diseases. These objections are based on:
A. Ethical and/or religious considerations
B. Economic considerations
C. A knowledge of the limitations of available techniques
D. A desire to relieve human suffering
19. Two patients suffering from a genetic disorder were successfully treated by somatic gene therapy in the US. Somatic gene therapy involves:
A. Introducing a functional gene into an affected tissue or group of cells
B. Homologous recombination
C. The gene gun
D. Introducing a functional gene into embryo stem cells
20. The gene prolactin in turkeys is associated with maternal behavior. It has its name due to its resemblance to the mammalian prolactin gene, which is also associated with maternal behavior. The relationship between the turkey and the mammalian genes is likely to be one of:
A. Identity over the entire genomic sequence.
B. Homology over the entire genomic sequence.
C. Homology among introns.
D. Homology among exons.
21. Regions of greatest similarity between genes with homologous functions mostly do not occur:
A. in conserved domains.
B. at the 3' untranslated end.
C. in the case of enzymes, at the sequence encoding the active site.
D. in the case of receptor proteins, at the binding site.
22. Levels of turkey prolactin are correlated with the egg laying and incubation phases of the hen's reproductive cycle. Based on its resemblance to the mammalian gene, where it is associated with milk production, do you expect:
A. high levels of prolactin at the time of egg laying?
B. low prolactin levels at the broodiness phase when the hen sits on the developing eggs?
C. high prolactin levels at the time of broodiness?
D. no change in prolactin levels in the transition from egg laying to broodiness?
23. Efforts to control malaria caused by parasitic protozoa harbored by the genus Anopheles stephensi (mosquito) has shifted from antibiotic and insecticide development to a molecular genetic approach. This change of approach is most likely due to:
A. The appearance of antibiotic-resistant parasites and insecticide -resistant mosquitoes.
B. The greater fame of molecular geneticists compared to pharmacologists.
C. A shortage of drugs that are used to treat malaria.
D. The reluctance of the drug companies to market expensive products.
24. Antibiotic-resistant parasites have most likely appeared because of:
A. overuse of antibiotics leading to selection for resistant strains of the parasite.
B. the appearance of stronger mosquitoes.
C. the appearance of new pathways for antibiotic degradation in the mosquito.
D. antibiotic biosynthesis in the parasite.
25. It has been found that the first line of immune response mounted by the mosquito to invasion by the parasite is the production of nitric oxide, which also functions as a defense molecule in vertebrates. One possible strategy that is being explored for malaria control is to engineer mosquitoes with a superior immune response that will have the capacity for a successful defense against the invading parasite. In order for this strategy to succeed, these transgenic mosquitoes must:
A. overrun the natural mosquito population in areas where malaria is a threat.
B. succumb to the threat of the natural mosquito population in areas where malaria is a threat.
C. bite malaria patients.
D. bite people at risk for malaria.
26. A common form of immunization against bacterially caused infectious disease involves the use of live vaccine. Live vaccine is:
A. a low dose of the infectious bacteria administered as prophylactic.
B. a dose of the bacterial strain in a modified form which retains immunogenicity but is not pathogenic.
C. a low dose of the toxin that is produced by the bacterium.
D. a sample of cells from a patient who recently recovered from the disease.
27. One method of disarming bacterial pathogenicity is by transposon mutagenesis. To use this technique in the creation of a vaccine, some prior knowledge is required.
A. The sequence of the transposon must be known.
B. Its site of insertion in the bacterial genome must be known.
C. The gene responsible for bacterial pathogenicity must be known.
D. Transposon restriction sites must be known.
28. In order to have the Food and Drug Administration approve a transgenic bacterium for use in a human vaccine, the exact nature of the mutation must be known and, most importantly, the probability of its reversion to wild type. Which of the following mutations is the FDA least likely to approve?
A. Point mutations
D. Chromosomal rearrangements
29. A genetic predisposition to some colon cancers has been traced to a recessive gene encoding a protein involved in DNA mismatch repair. Nonetheless, heterozygous individuals are known to be increasingly at risk for the disease as they age. This is likely due to:
A. somatic mutations in the damaged copy of the gene.
B. germline mutations in the undamaged copy of the gene.
C. an accumulation over time of mutations in a clone of cells with two damaged copies of the gene.
D. eating fatty, high salt, foods.
30. It is possible, at this time, to control the point of insertion of an introduced gene into
A. a bacterial genome
B. a plant genome
C. an animal genome
D. (B) and (C)
31. The human eye has evolved to respond to a broad range of light intensities from moonlight to full sun. This versatility is made possible by:
A. Rapid adjustment of rhodopsin pool sizes.
B. Positive feedback of signals involving changes in intracellular calcium.
C. Modulation of signal amplification strengths.
D. None of the above.
32. Patients who suffer from phenylketonuria are homozygous for a mutant gene encoding a deficient form of phenylalanine hydroxylase. Heterozygous individuals ("carriers") show a normal phenotype. This is because:
A. The recessive gene is not expressed in carriers.
B. The normal gene is haplo-insufficient.
C. The dominant allele produces sufficient protein in carriers to sustain normal function.
D. The gene product of the abnormal allele is preferentially degraded in carriers.
33. Cells isolated from a carrot were grown in suspension and eventually developed into a mature carrot plant. For this to occur, the original cell must have initially:
A. Undergone meiosis
C. Activated its senescence genes.
D. Undergone photomorphogenesis.
34. Dolly the sheep was cloned by introducing a nucleus from the mammary gland of a mature ewe into an enucleated egg cell. Dolly, therefore, has:
A. A nuclear genome from one cellular source and an organellar genome from another source.
B. Nuclear and mitochondrial genomes from the same cellular source.
C. A haploid genome.
D. More potential to transmit genetic variation to her offspring than animals produced as a result of sexual reproduction.
35. Sex-linked traits are expressed:
A. Only in males.
B. Only in females.
C. Most commonly in males and rarely in females.
D. Primarily in people of Eastern European descent.
36. Specific targeting sequences direct:
A. mRNAs from the nucleus to their place of expression in the mitochondrion or the chloroplast.
B. Completed polypeptide chains from the cytosol to nuclei, mitochondria and chloroplasts.
C. RNA splicing.
D. Newly degraded protein fragments to lysosomes.
37. During RNA splicing:
A. Exon lariats are formed.
B. Primary transcripts are formed.
C. Specific sequences are recognized at intron-exon borders.
D. Transposons are inserted into primary transcripts.
38. The first stages in the origin of life probably involved:
A. The appearance of autocatalysis.
B. The appearance of DNA.
C. The appearance of proteins.
D. The appearance of molecular oxygen.
39. Drosophila with a wild type white gene have red eyes. Flies with a mutant white gene have white eyes. This confusing nomenclature arose because:
A. The geneticist who made the original observation was mistaken.
B. The geneticist who made the original observation was not an English speaker.
C. The gene was initially discovered in its mutant form.
D. The red pigment in the eyes of wild type flies is not synthesized under the conditions of the original observation.