Florida Atlantic University PCB 3063 Genetics Exam 4. 50 MCQ.

Genetics Exam 4 1. A 900 bp open-reading frame (ORF) that begins with an AUG start codon and ends with a stop codon would encode a polypeptide containing __________ amino acids. A. 100 B. 900 C. 299 D. 300 E. None ...

Genetics Exam 4 1. A 900 bp open-reading frame (ORF) that begins with an AUG start codon and ends with a stop codon would encode a polypeptide containing __________ amino acids. A. 100 B. 900 C. 299 D. 300 E. None of the above 2. Helix-turn-helix and zinc fingers are structural motifs commonly associated with A. Enhancers and promoters B. DNA binding proteins C. Methylases (the enzymes that methylate DNA) D. Prokaryotic sigma factor E. Select this answer if more than one of the choices A-D are correct. 3. Which of the following statements regarding enhancers is true? A. Enhancers have been identified upstream of the transcriptional start site, downstream of where transcription terminates and even within introns of the transcription unit. B. Enhancers are commonly found in both prokaryotic and eukaryotic cells. C. Enhancers function by direct DNA-protein interaction with the basal transcription apparatus. D. Enhancers function by decreasing the rate of transcription. E. Select this answer if more than one of the statements A-D are true. 4. Dominant mutations in a gene that cause it to be over-expressed or expressed t the wrong time or in the wrong tissue are known as A. Gain-of-function mutations B. Loss-of-function mutations C. Recessive lethal mutations D. Homeotic mutations E. None of the above. 5. Recessive mutations in genes controlling development are usually due to a(n) A. Gain-of-function mutation B. Over-expression of the gene product C. Loss-of-function mutation D. Expression of the gene at the wrong time E. Select this answer if none of the answers A-D are correct. 6. The proteome of a specific cell type refers to A. The collection of all proteins expressed by that type of cell/ B. The orthologous proteins expressed in a specific cell type from two different species. C. Rapid degradation of selected proteins within the cell type. D. The variation in proteins expressed within a specific cell type among different individuals within the population. E. Select this answer if none of the choices A-D are correct. 7. A __________ is a group of evolutionary related genes that arose through repeated evolution of an ancestral gene. A. Microarray B. Multigene family C. Proteome D. Haplotype E. Contiguous segment 8. Jr. Scientist used RNA interference technology to “knock-down” expression of Dnmt3 in honeybee larvae. Hint: Dnmt3 encodes a methylase. Which of the following is an expected outcome? A. Male drones will develop due to genomic imprinting. B. Female workers will develop because increased DNA methylation blocks expression of specific genes needed for development of a queen bee. C. Female queens will develop because decreased DNA methylation allows expression of genes needed for development of a queen bee. D. Male drones will develop due to changes in expression of genes involved in sex determination. E. Female workers will develop due to changes in chromatin structure associated with altered patterns of histone acetylation. 9. The immense diversity of IgG antibodies is accomplished by using only a few hundred genes. The molecular mechanism involves: A. Permanent genomic DNA rearrangements in the B-cells of the immune system. B. Permanent genomic DNA rearrangements in both the B-cells of the immune system and germ line cells. C. Changes in chromatin confirmation due to DNA methylation. D. Differential splicing of the IgG pre-mRNA so that the variable (V) and joining (J) parts of the polypeptide are used in different combinations with the constant (C) portion. E. Select this answer if more than one of the choices A-D are correct. 10. TG and AC mutations are examples of A. Transition mutations B. Transversion mutations C. Translation mutations D. Transcription mutations E. Conditional mutations 11. Which of the following can contribute to development of some forms of cancer? A. Mutations in DNA repair mechanisms. B. Mutations affecting proper chromosome segregation. C. Mutations affecting DNA methylation. D. Mutations affecting telomerase activity. E. Select this answer if more than one of choices A-D are correct. 12. What information can be learned from the structure of a protein? A. The location of the active site of an enzyme B. Possible interaction sites with other molecules C. Targets for potential drugs D. A source of insight into the function of an unknown protein E. Select this answer if more than one of the choices A-D are correct. 13. Which of the following is (are) false regarding retinoblastoma? A. Development of retinoblastoma involves Rb-1, which is a tumor-suppressor gene. B. Initially, it was thought that retinoblastoma was due to a dominant mutation in the Rb-1 gene based on the pattern of inheritance observed from pedigree analysis. C. Retinoblastoma is always the result of dominant gain-of-function mutations in both alleles of the Rb-1 gene of a retinal cell. D. Retinoblastoma develops from a single cell of the retina that is homozygous for a loss-offunction mutation in the Rb-1 gene. E. Select this answer if all of the choices A-D are true. 14. After DNA synthesis is complete, improperly paired bases can be removed and replaced with the proper base pair by the DNA repair process called A. Proofreading B. Photoreactivation C. The SOS repair system D. Mismatch repair E. None of the above 15. Ultraviolet light damages DNA by A. Forming covalent bonds between adjacent pyrimidines. B. Depurinating DNA. C. Alkylating DNA. D. Forming covalent bonds between adjacent adenosine bases. E. Select this answer if more than one of the choices A-D are correct. 16. What is the function of DNA glycosylases? A. Recognize and cleave phosphodiester bonds in DNA. B. Recognize and remove damaged bases from DNA by cleaving the glycolytic bond joining the base to the 1’ carbon of the sugar. C. Reattach the two parts of DNA that result from double-strand breaks. D. Remove pyrimidine dimers from DNA to E. coli that result from exposure to UV light. E. Prevent strand slippage during DNA replication. 17. The nucleotide excision repair process involves A. Nicking DNA on both sides of the damaged site, which leads to removal of an oligonucleotide that contains the damaged DNA. B. Nicking DNA upstream from the damage, which is then removed and replaced with newly synthesized DNA by DNA Polymerase I. C. Crossing over between homologous chromosomes. D. Repairing a wide range of DNA damage that distorts the overall shape of the DNA. E. Select this answer if more than one of the choices A-D are correct. 18. 5-methylcytosine bases in eukaryotic DNA are “hotspots” for mutations because deamination A. Produces nucleotides that are exceptionally reactive with alkylating agents such as EMS. B. Produces adenine, a legitimate nucleotide base. C. Leads to stable base pairing with either guanine or adenine and thus leads to increased levels of transition mutations. D. Prevents the mismatch repair system from correcting the mutation since the damaged base is biochemically identical to thymine, a legitimate base in DNA. E. Select this answer if none of the answers A-D are correct. 19. Which of the following is false regarding hemimethylated DNA? A. It exists for a brief period of time immediately following completion of DNA replication. B. Contains bases modified by methylation on only one strand of the duplex DNA. C. Is used by the mismatch DNA repair system to distinguish parental DNA from newly synthesized DNA. D. In eukaryotic cells, the methylation is mainly on adenine nucleotides. E. Select this answer if all of the choices A-D are true. 20. Which of the following mutations would prevent activation of the SOS repair system in response to extensive DNA damage that resulted in significant amounts of single-stranded DNA, as might occur from UV exposure? A. A LexA protein that is resistant to cleavage by the protease activity of RecA. B. A LexA protein that does not bind to the “SOS Box” DNA. C. A RecA protein that was unable to activate its associated protease activity. D. A RecA protein that is no longer bound to single-stranded DNA. E. Select this answer if more than one of the answers A-D are correct. 21. An AP-endonuclease A. Removes purines from specific types of DNA binding proteins. B. Adds a methyl group to the 2’-carbon of the deoxyribose of an apurinic site in DNA. C. Is one of the enzymes needed to remove uracil bases in DNA that often results from deamination of cytosine. D. Is important for proper functioning of the mismatch repair system (Mut HSL). E. Select this answer if none of the choices A-D are correct. 22. RNA silencing and post-transcriptional gene silencing is also known as A. Protein degradation B. Transcriptional stalling C. RNA splicing D. Transcriptional repression E. RNA interference 23. What type of enzyme would most likely be associated with decreased gene expression? A. DNA methyltransferase B. DNA demethylase C. DNA polymerase D. DNA ligase E. DNAse 24. Which of the following is an important reason that metagenomics is particularly useful for studying microbes? A. Many bacteria that cannot be cultured in the laboratory can now be studied. B. The composition of natural microbial communities can be reconstructed. C. The microbiome of different individuals can be compared to understand the basis of infectious diseases. D. Previously unknown species of bacteria and new gene families have been discovered. E. Select this answer if more than one of the answers A-D are correct. 25. Which of the following is (are) false concerning microarray technology? A. A microscope is needed to gather the data since each spot of DNA is microscopic in size. B. The technique is limited to examining levels of gene expression (as measured by the amount of corresponding mRNA) for no more than 10 genes in a single experiment. C. The technology works the best with organisms whose genomes have been fully sequenced. D. The technology for making the microarray is derived from the methodology used to manufacture computer chips. E. Select this answer if more than one of the choices “A-D” are false concerning microarray technology. 26. Jr. Scientist has tentatively identified a human ortholog of a yeast gene. He determines the mRNA sequence obtained by transcription and splicing of the yeast gene and the human gene. Furthermore, he compares the corresponding genomic DNA sequences, as well as the amino acid sequences for the polypeptides encoded by the ORF of each gene. He would expect the greatest sequence similarity from comparisons of the: A. mRNA sequences B. Protein sequences C. Genomic DNA sequences D. Both “A” and “B” will give him equivalent sequence similarities. E. Comparisons of choices A, B, and C will give him equivalent sequence similarity. 27. A homeobox (also called homeodomain) is a(n) A. 180 nucleotide sequence to which homeotic DNA binding proteins attach. B. 180 nucleotide sequence that codes for a 60 amino acid DNA binding motif. C. Protein involved in the control of meiosis. D. Gene that codes for one of the maternal-effect genes. E. None of the above. 28. Which class of genes is the result of an ancient gene duplication? A. Orthologs B. Paralogs C. Heterologs D. Pseudologs E. Lincolnlogs 29. A mutation that changes the nucleotide sequence of a codon, but does not change the amino acid specified by the altered codon is an example of a A. Conditional mutation B. Permissive mutation C. Missense mutation D. Nonsense mutation E. Silent mutation 30. Mutations in homeotic genes in Drosophila result in A. Embryos with defective pole cells. B. Transformation of one body segment into another. C. Disruption of meiosis. D. Disruption of development at the anterior end of the early embryo. E. Select this answer if none of the choices A-D are true. 31. A gene that influences early development through its expression in the mother and the gene product is found in the oocyte prior to fertilization is called a A. Zygotic gene B. Maternal-effect gene C. Segment-polarity gene D. Pair-rule gene E. Gap gene 32. Which of the following order of gene groups is CORRECT for normal Drosophila development? 1. Gap genes 2. Homeotic genes 3. Pair-rule genes 4. Segment-polarity genes 5. Egg-polarity genes A. 1, 2, 3, 4, 5 B. 4, 2, 5, 1, 3 C. 3, 1, 2, 5, 4 D. 5, 2, 4, 3, 1 E. 5, 1, 3, 4, 2 33. The mismatch repair system of E. coli distinguishes the original DNA strand from the newly synthesized DNA by A. The absence of methylated DNA on either strand. B. The presence of methylated DNA on the original DNA strand. C. The presence of methylated DNA on the newly synthesized strand. D. The presence of methylated DNA on both DNA strands. E. Select this answer if none of the choices A-D are true. 34. Suppose a research study shows that people who suffer from hyper-anxiety are homozygous for a mutation in the Always on Edge (AOE) gene. Individuals without this disorder have the following sequence at the beginning of the translated region of their AOE genes – 5’-ATG ACG TTT GAA ATT CAG TCT AGA-3’ (Met Thr Phe Glu Ile Gln Ser Arg). Affected individuals have the following sequence – 5’-ATG ACG TTT GAA ATT TAG TCT AGA-3’ (Met Thr Phe Glu Ile STOP). The mutation identified is most likely a __________ mutation. A. Missense B. Gain of function C. Nonsense D. Frameshift E. Deletion 35. Suppose Jr. Scientist discovered a new species of wolves living in the arctic. The animals have all white fur except for black fur on the tips of the ears, paws, and tail. At least one of the genes involved in the synthesis and deposition of the black pigment probably has a A. Gain of function mutation B. Temperature sensitive mutation C. Hypermorphic mutation D. Null mutation E. Deletion mutation 36. When regions around genes become hyper-sensitive to DNase, this is an indication that those regions of chromatin are more likely to be A. Transcriptionally active B. Condensing to form heterochromatin C. Binding to the single-strand binding proteins D. Destabilizing and transcriptionally inactive E. Becoming highly methylated by a methylase 37. Which of the following is false regarding morphogens? A. Morphogens establish chemical gradients that affect gene expression in specific regions of the developing embryo. B. Morphogens often function as transcriptional activators. C. Morphogens are typically found in the sperm prior to fertilization. D. Morphogens play critical roles in establishing body pattern formation during early development of the embryo. E. Select this answer if more than one of the choices A-D are false. 38. Oncogenes are __________ mutations in normal cellular genes called __________ genes whereas tumor-suppressor genes have __________ mutations that inactivate genes involved in cell proliferation. A. Recessive; proto-oncogenes; dominant B. Dominant; proto-oncogenes; recessive C. Loss of function; HOX; dominant D. Gain of function; HOX; recessive E. Recessive; maternal effect; recessive 39. Following fertilization of a Drosophila embryo, the __________ protein forms a morphogen gradient with the highest concentration at the __________ of the embryo. A. Bicoid; anterior B. Nanos; anterior C. Hunchback; dorsal D. Twisted; ventral E. Homeotic; segmentation boundaries 40. The inherited autosomal recessive human disease called xeroderma pigmentosum results from a defect in the A. Mismatch repair system B. Photoreactivation system C. Uracil DNA glycosylase system D. Nucleotide excision repair system E. Select this answer if none of the choices A-D are correct. 41. Most transposable elements are flanked by short direct repeats. How are these direct repeats formed? A. The direct repeats result from repairing the staggered cuts created by the transposase as part of the mechanism of inserting the transposable element. B. The direct repeats are the termini of the transposable element. C. The direct repeats form during activation of the protease activity associated with RecA activity used by cells to prevent insertion of the transposon. D. Direct repeats only occur if the transposable element inserts itself into the DNA at a replication fork during DNA synthesis. E. Direct repeats only occur when the transposable element inserts itself into genomic DNA containing repetitive DNA. Extra Credit 42. Many tumor cells are able to divide uncontrollably in cell culture in the laboratory. Some of these cell lines have genomes with a mutant tumor suppressor gene. By adding a wild-type copy of this tumor suppressor gene to the genomes of these cells, they have a reduced ability to divide in culture. In contrast, adding a wild-type copy of a proto-oncogene to the genomes of a tumor cell line with an activated oncogene doesn’t have any effect on the uncontrolled cell division shown by this line. Which of the following statements best explains why adding a wild-type proto-oncogene doesn’t affect cell division in these cell lines? A. Most point mutations that produce activated oncogenes are dominant gain-of-function mutations. B. Many proto-oncogenes encode proteins that act to promote apoptosis. C. Many proto-oncogenes encode proteins involved in DNA repair. D. Many proto-oncogenes are inherited as recessive mutations. E. Most protein products of proto-oncogenes do not have a role in cell division. 43. Posterior development of a Drosophila embryo requires the Nanos protein in the egg prior to fertilization. Otherwise, the embryo will develop two heads if Nanos protein is not present. The loss-of-function nano- mutation is recessive and exhibits a maternal effect. Which of the following correctly describes the embryos produced from a cross between a nano+/nano- male and a nano-/nano- female? A. All embryos will be normal. B. All embryos will have two heads. C. Three-fourths of the embryos will have two heads. D. One-half of the embryos will have two heads. E. One-fourth of the embryos will have two heads.