Biology 303 EXAM III

BIOL 303 EXAM III 12/04/06 NAME______

This exam consists of 40 questions worth 2.5 points each. Please indicate the single best choice for each question on the separate answer sheet. Be sure to enter your student number on the answer sheet. Good luck! ______

1. What is the term which refers to a contiguous set of bacterial genes which are under coordinate control?

1. lysogen. 2. prototroph. 3. operon. 4. allosteric.

2. What effect on transcription of the structural genes of the lac operon is observed when lactose is present in the environment?

1. Transcription does not occur. 2. The genes are transcribed for only a single generation and then are shut off. 3. Lactose represses the synthesis of the repressor. 3 4. Transcription of the structural genes is induced when lactose is present.

3. What is the function of cAMP in regulation of the lac operon?

1. activates a repressor protein 2. activates an activator protein 3. inactivates a repressor protein 4. inactivates an activator protein

4. Consider a bacterial strain that has a mutant lac repressor that cannot bind the lac operator region. This strain likely

1. synthesizes lactose. 2. displays inducible expression of the lac operon. 3. displays constitutive expression of the lac operon. 4. does not catabolize lactose. Use the following diagram of the lac I gene and lac operon for questions 5 and 6. (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator)

I P O Z Y A

5. Where would the lac repressor be bound in a (nonmutant) E. coli cell that is growing in low glucose and high lactose?

1. P 2. O 3. P and O 4. the repressor would not be bound

6. Which parts of the DNA region shown in the diagram encode proteins?

1. P 2. P, O, Z, Y, A 3. I, Z, Y, A 4. I, P, O, Z, Y, A

7. When referring to attenuation in regulation of the tryptophan operon it would be safe to say that when there are high levels of tryptophan available to the organism

1. the tryptophan operon is being transcribed at relatively high levels. 2. translational termination is likely. 3. transcriptional termination is likely. 4. tryptophan is inactivating the repressor protein.

8. A type of DNA sequence in eukaryotes that helps to regulate transcription, may be tissue specific, and may exert control over a gene that is a great distance away is called

1. a promoter. 2. a Shine-Dalgarno sequence. 3. a TATA box. 4. an enhancer. 9. Feeding mammals with azacytosine can alter gene expression because

1. gene expression is not affected by chromatin structure. 2. incorporation of azacytosine into DNA brings about undermethylation of DNA which generally turns on genes. 3. incorporation of azacytosine into DNA brings about increased methylation of DNA which turns off genes. 4. none of the above.

10. Which statement about RNA splicing in eukaryotes is true?

1. splicing does not represent a potential level of regulation of gene expression. 2. splicing occurs in the cytoplasm. 3. every RNA molecule produced in a eukaryotic cell undergoes splicing. 4. the same transcript may be spliced in different ways to ultimately yield different translation products.

11. In eukaryotes, actively transcribed chromatin is

1. DNase insensitive. 2. in a highly condensed form 3. usually DNase sensitive. 4. sometimes referred to as heterochromatin.

12. The term "chromatin remodeling" refers to

1. alteration of chromatin structure in association with transcription. 2. a process that only bacteria perform since they contain no nucleus. 3. a process that is exclusively associated with transcription by reverse transcriptase in eukaryotes. 4. alteration in chromatin structure to facilitate loading and translation by ribosomes and, thus, enhance gene expression.

13. What modification neutralizes the charges on histones and loosens up the interactions between histones and DNA?

1. phosphorylation 2. methylation 3. acetylation 4. polyadenylation 14. When comparing regulation of gene expression in eukaryotes versus prokaryotes, which of the following processes seems to be the most similar between the two?

1. transcription. 2. RNA splicing regulation. 3. intron/exon shuffling. 4. 5'-capping.

15. DNA methylation may be a significant mode of genetic regulation in eukaryotes. Methylation refers to

1. altering RNA polymerase activity by methylation of RNA polymerase 2. altering translational activity especially of highly methylated tRNAs. 3. alteration of DNA polymerase activity by addition of methyl groups to glycine residues. 4. addition of methyl groups to the cytosine of CG doublets

16. Two types of post-transcriptional modifications that take place in the mRNA of eukaryotes are

1. the addition of a poly T sequence at the 5' end of the gene and the addition of a poly U tail at the 3' end. 2. addition of a poly A sequence at the 5' end and the addition of a “cap” at the 3' end of the RNA transcript. 3. the addition of a cap at the 5' end of the transcript and the addition of a poly A sequence at the 3' end of the message. 4. the excision of the introns and the addition of a cap to the 3' end.

17. The "Philadelphia chromosome"

1. is a movie starring Tom Hanks. 2. is a specific translocation implicated in chronic myelogenous leukemia. 3. results from a gene amplification event. 4. is an example of overexpression of an oncogene that is otherwise unaltered. 18. Which statement about cancer is true?

1. the development of cancer usually involves a single mutation. 2. "loss of heterozygosity" (LOH) is usually discussed in relation to tumor suppressor genes. 3. oncogenes and proto-oncogenes are the same thing. 4. people with inherited predisposition to cancer are usually born homozygous for a defective tumor suppressor gene.

19. What is the name of the type of protein that combines with cyclins to exert local control of the cell cycle?

1. cyclin dependent kinase 2. phosphatase 3. ATPase 4. telomerase

20. An individual develops retinal tumors in both eyes. This is most likely due to

1. Wilms tumor. 2. the nonfamilial form of retinoblastoma. 3. cancer in another part of the body that has metastasized to the eye. 4. the familial form of retinoblastoma

21. What is the name of the protein that, among other things, regulates the entry of cells into S phase, is mutated in most cancers, and is known as the “guardian of the genome?”

1. p34 2. p102 3. cyclin 4. p53

22. The development of the anti-cancer drug “Gleevec” was facilitated by

1. gross chromosomal instability seen in the FAP form of colon cancer 2. microsatellite instability seen in Hereditary Nonpolyposis Colorectal Cancer 3. LOH via gene targeting. 4. the discovery of a specific translocation associated with chronic myelogenous leukemia

23. What is the function of dideoxynucleotides in Sanger DNA sequencing?

1. They act as primers for DNA polymerase. 2. They act as primers for reverse transcriptase. 3. They cut the sequenced DNA at specific sites. 4. They stop synthesis at a specific site, so the base at that site can be determined.

24. Two especially useful characteristics for a cloning vector to have are

1. lots of cloning sites and an antibiotic resistance gene. 2. virulence and antigenicity. 3. ability to integrate into the host chromosome and then cause death. 4. reverse transcriptase and ligase activities.

25. Which of the following is not needed in order to amplify a DNA fragment by PCR?

1. a set of primers. 2. knowledge of the complete nucleotide sequence of the fragment to be amplified. 3. a DNA polymerase. 4. deoxynucleotide triphosphates.

26. Nucleic acid blotting is widely used in recombinant DNA technology. In a Southern blot one generally

1. hybridizes filter-bound DNA with a DNA probe. 2. hybridizes filter-bound RNA with a DNA probe. 3. examines amino acid substitutions with radioactive probes. 4. cleaves RNA with restriction endonucleases.

27. The phenomenon known as “RNAi” (RNA interference) is used experimentally to

1. reduce expression of a specific target gene. 2. reduce transcription rate from a specific gene promoter. 3. interfere with replication. 4. enhance gene expression. Use the following diagram for questions 28 and 29. ddATP reaction ddTTP reaction ddCTP reaction ddGTP reaction

28. A fragment of DNA was sequenced and the gel pattern shown above was obtained. For the strand of DNA that was synthesized in the sequencing reaction, what base was incorporated first (closest to the primer)?

1. G 2. A 3. C 4. T

29. What was the sequence of the DNA primer used in the sequencing reaction?

1. 5' GCTAGCA 3' 2. 5' ACGATCG 3' 3. 5' TGCTAGC 3' 4. Can’t tell!

30. Regarding the sequencing of genomes, which statement is true?

1. most of the human genome has been sequenced. 2. no eukaryotic genome has yet been sequenced. 3. DNA sequencing has revealed a complete lack of polycistronic transcription units in eukaryotic genomes. 4. fewer than 300 genomes have been sequenced. 31. Compared to prokaryotic chromosomes, eukaryotic chromosomes in general

1. are larger 2. have interrupted genes 3. display lower gene density 4. all of the above

32. Based on the most recent analysis of the sequence of the human genome, which is closest to the estimated number of human genes?

1. 2,000 2. 25,000 3. 100,000 4. 500,000

33. Analysis of eukaryotic genomes has revealed that

1. large segments of genomes have undergone duplication during evolution. 2. genes are never found within the introns of other genes. 3. genome size always correlates well with organism complexity. 4. transposons are rarely found in genomes.

34. Analysis of the human genome has revealed that about half (or maybe more) of the human genome seems to be composed of

1. protein-coding genes. 2. ribosomal RNA genes. 3. transposons or transposon-like elements. 4. satellite sequences.

35. The alpha and beta globin gene families

1. each contains one single gene. 2. contain genes with no introns. 3. each contains one or more “pseudogenes.” 4. are within the heterochromatin portion of the human genome. 36. You have isolated several mutant strains of mice that are eyeless. After performing a variety of crosses and examining the offspring, you learn that wildtype offspring are produced by crossing eyeless strain A with eyeless strain B, wildtype offspring are produced by crossing eyeless strain A with eyeless strain C, and wildtype offspring are produced by crossing eyeless strain B with eyeless strain C. What can you conclude?

1. Only a single gene is involved in eye development in mice. 2. There are at least three genes involved in eye development in mice. 3. The mutation in strain A is dominant. 4. Mice do not need eyes to see.

37. If you wanted to check the level of a specific mRNA produced in a certain tissue, you might do a

1. Southern blot. 2. Western blot. 3. Southwestern blot. 4. Northern blot.

38. A “knockout mouse” is

1. a mouse trained to box. 2. a really good-looking mouse. 3. a mouse in which a specific gene has been altered to block expression. 4. produced by cloning another mouse.

39. When comparing a knockout mouse with the technique of RNAi using transfection with siRNA,

1. the effect of RNAi is permanent, while the phenotype of a KO mouse is temporary. 2. the effect of RNAi is temporary while the phenotype of a KO mouse is permanent. 3. RNAi can achieve complete loss of gene activity, while a KO mouse displays only partial loss of expression of the target gene. 4. RNAi is less useful because it can only be done in yeast cells. 40. Which of the following is achievable (or potentially achievable) using current biotechnology?

1. Developing plants that can serve as “edible” vaccines. 2. Developing transgenic animals that produce pharmaceutical products in their milk. 3. Performing prenatal diagnosis for sickle-cell anemia. 4. All of the above.

That’s all! QUESTION NUMBER CORRECT ANSWER

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