Test 2 Spring 2001

Test 2 Spring 2001 - Bil 255 GLASER Spring 2001 2001...

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Unformatted text preview: Bil 255 GLASER Spring 2001 2001 Directions: T est #2 – Form 0 04 April Choose the BEST answer from among the choices given. 1. When DNA synthesis is initiated at an origin of replication, the two parental strands are replicated (think carefully) ? a) In opposite directions b) In same direction c) One continuously and one discontinuously d) a and c apply e) b and c apply 2. DNA synthesis is always initiated by ? a) An RNA primer b) A guanosine cap c) A deoxyribonucleotide triphosphate 3. Mistakes in DNA synthesis are, to a large extent, avoided because DNA polymerase has ? a) Proofreading function b) Mismatch repair enzymes correct DNA after synthesis apply c) Both a and b 4. Some mutations (base changes in DNA) are phenotypically silent (i.e., have no biological effect). Their most likely location is in ? a) Exons b) Introns 5. RNA is synthesized by copying DNA ? a) Both strands of DNA are transcribed to yield double stranded RNA b) At any position in genome only one strand of DNA is transcribed 6. RNA molecules have ? a) No secondary structure 7. Messenger RNA ? a) Codes for proteins b) Fold at random b) c) Can fold using base pairing rules into unique structures Is the only RNA transcribed from DNA c) a and b apply 8. Messenger RNA’s differ in procaryotes and eucaryotes ? a) Procaryotic messages are polycistronic (code for more than one protein) and eucaryotic messages often only code for one protein b) Procaryotic messages code for one protein, eucaryotic messages code for multiple proteins 9. Eucaryotic messengers RNA’s have ? a) A poly A tail at 5' end and a methyl G cap at 3' end b) A poly A tail at 3' end and a methyl G cap at 5' end 10. Exons are assembled into mature mRNA ? a) Same sequence in every cell b) Alternative splicing of primary transcripts occurs in different cell types 11. The boundary between exons and introns is ? a) Precisely defined so that splicing always occurs at the same site b) The boundary is variable and splicing can occur in many regions for the same exon/intron boundary 12. The nucleotide sequence of a small fragment of messenger RNA is AUGCUCAGCGUU. The genetic code is attached to the last page of the exam. You conclude that the amino acid sequence of the protein coded by this message contains the sequence ? a) Cys-Ser-Ala b) Met-Leu-Ser c) There is not enough information to decide 13. The function of tRNA’s is to translate mRNA sequence ? a) There is only one tRNA for each amino acid c) There are multiple tRNA’s for all amino acids b) There are multiple tRNA’s for some amino acids Bil 255 Test # 2 – Glaser – Form 0 – pg 2 14. In general, the DNA in each cell of the body of a eucaryotic organism, for example man, is ? a) Different in each cell type b) The same in each cell type 15. Amino acids are covalently attached to tRNA to form amino-acyl tRNA’s ? a) The amino acid is attached to the anticodon on tRNA b) The amino acid is attached to 3' hydroxyl at terminal adenine on tRNA c) Neither statement applies 16. Proteins and mRNA’s, once made in a cell ? a) Remain for the life time of the cell b) Are continuously degraded at rates specific for each molecule 17. The minimal components required for function of a eucaryotic chromosome are ? a) Centromere b) Replication origin c) Telomere and telomerase d) All apply 18. Proteins that control gene expression, i.e., frequency of transcription, bind to ? a) Single bases in DNA b) Multiple bases in DNA c) Bind to DNA in either the major or minor groove d) a and c apply e) b and c apply 19. In procaryotes the synthesis of enzymes required to make essential amino acids/vitamins/sugars depends on the availability of these in the fluid in which cells grow. Repressors are best described as ? a) Proteins that control nutrient uptake by cells b) Proteins that bind to DNA at promoter regions, dependent on concentration of specific ligands in cells, for example, an amino acid c) Are a component of RNA polymerase 20. In eucaryotic cells all RNA molecules are ? a) Made by the same RNA polymerase b) Made by different RNA polymerases 21. A given regulatory protein may ? a) Control expression of a single gene b) Can control expression of multiple genes 22. When E. coli is grown in the presence of streptomycin (an antibiotic), approximately 5 colonies grow from 108 cells. A strain of E. coli defective in the proofreading mechanism of DNA polymerase grows poorly under normal conditions. When tested for its ability to grow in the presence of streptomycin you expect: How many colonies per 108 cells ? a) 5 colonies b) > 5 colonies c) < 5 colonies 23. A strain of E. coli containing an integrated F-plasmid in the genomic DNA is also resistant to rifampicin, and able to grown in the absence of tryptophan. You observe that rifampicin resistance is transferred, at high frequency while the ability of the recipient cells to grown in the absence of tryptophan is observed with low frequency. You conclude ? (pick best answer) a) The two genes are on different chromosomes b) The location of rifampicin resistance gene is close to the site of integration of F-plasmid and the tryptophan gene is distal c) The location of rifampicin resistance gene is close to the beginning site for DNA transfer and the tryptophan gene is remote from this site 24. You chemically link the amino acid alanine (Ala) labeled with 14C to the tRNA for leucine. You use this molecule in an in vitro system to synthesize a protein using the appropriate mRNA, ribosomes, etc. The initial coding sequence for this protein is : AUG-UUU-GCU-CUU-GCG You expect to find radioactive alanine ? (think carefully) a) In position 1 and 3 b) In position 3 c) In position 4 d) In position 5 25. Homologous recombination occurs between DNA molecules, which at the site of recombination have ? a) Highly different nucleotide sequences b) Identical or nearly identical nucleotide sequences Bil 255 Test # 2 – Glaser – Form 0 – pg 3 26. Retroviruses contribute to genetic diversity because ? (think carefully and pick the best answer) a) They contain RNA instead of DNA b) They contain reverse transcriptase c) Their genome is inserted as DNA into chromosomes d) During transcription and packaging of virus they sometimes (rarely) incorporate a host gene into viral particle as RNA 27. Restriction enzymes cleave DNA ? a) At random sites b) At unique sequences d) a and c apply e) b and c apply c) The sequence at the site is often a palindrome Note Questions 28 - 30 are related 28. You clone the portion of mouse DNA that codes for the enzyme hexokinase (involved in glycolysis), as well as, a small portion of adjacent DNA. You sequence a portion of this DNA and you use it to identify clones for the same DNA region (coding for hexokinase) from pig/human/horses/baboons, using hybridization and a radioactive oligonucleotide with the mouse sequence as a probe. In order to accomplish this you hybridize the protein to your clones at ? a) High stringency b) Low stringency c) It does not matter, either will work 29. Having obtained clones for the gene for hexokinase from mouse/pig/horse/baboon/human, you examine their pattern of cleavage by restriction enzymes. You expect the ? a) Pattern to be totally different b) Pattern of cleavage of baboon and human genes to be more similar than mouse and human c) Pattern of cleavage of baboon and human genes to be as different from each other as mouse and human 30. You completely sequence the hexokinase genes from all species and you compare the sequences, not only at nucleotide level, but also of the protein (i.e., hexokinase) for which they code. You expect ? a) More divergence in introns than in exons b) Less divergence in introns than in exons c) The amino acid sequence of protein to be more related than nucleotide sequence d) a and c apply e) b and c apply 31. You wish to code the gene for red hair, so everyone can look like Luis Glaser. You determine a partial amino acid sequence of a protein that determines hair color as : Ala-Phy-Gly-Gly-Leu and after looking up the genetic code (attached), you synthesize an oligonucleotide probe to identify the gene from a genome library. The oligonucleotide that you synthesize has the sequence : GCC-UUC-GGU-GGG-UUA and you fail to find, even after five years of work, any sign of the gene. You should have ? a) Come to class more often b) Synthesized a series of random oligonucleotides c) Synthesized all possible oligonucleotides that can code for the amino acid sequence above 32. The effect of cholesterol on a lipid bilayer is to ? a) Make it more fluid b) Restrict mobility 33. The region of a membrane protein that traverses the lipid bilayer is usually arranged on ? a) An extended chain of amino acids b) An α helix c) A pleated sheet 34. Tight junctions ? a) Promote movement of proteins in membranes 35. For all cells is ? a) Na+ inside > Na+ outside b) b) Restrict movement of proteins in membranes Na+ outside > Na+ inside Bil 255 Test # 2 – Glaser – Form 0 – pg 4 36. Glucose and mannose are monosaccharides of identical size (Mol wt. 180), yet glucose readily enters muscle cells and mannose does not. The concentration of glucose in the intracellular fluid (cytoplasm) is never higher than in extracellular fluid and often lower. Based on these observations, you expect glucose entry into muscles to be ? a) Via a pore b) By a glucose specific carrier c) by a Na+/glucose cotransporter (symport) 37. Which of the following statements is correct regarding ATP driven pumps ? a) The only ATP driven pump is the Na+/K+ ATPase b) Eucaryotes contain a variety of ATP driven pumps including Na+/K+ ATPase, Ca++ ATPase & H+ ATPase c) All ATP driven pumps are in the cytoplasmic membrane d) b and c are correct 38. Ribozymes are ? a) Enzymes that cleave ribonucleotide c) Enzymes that cleave RNA at specific sequences d) b) RNA's with catalytic activity a and b apply e) b and c apply 39. Na+/H+ antiport is one of the primary regulators of intracellular pH. When the fluid surrounding a cell contains no Na+ would you expect the cell’s cytoplasm ? a) To become more acid b) To become more alkaline 40. A particular cell type can potentially utilize 3 different regulatory proteins that control gene expression to generate different phenotypes by utilizing any possible combination of these proteins from 0 to 3. How many potential phenotypes can arise ? a) 3 b) 6 c) 8 d) none of these is correct 41. Consult the following restriction fragment length polymorphism made by hybridization to a DNA probe after digestion of human DNA with restriction enzyme. Think carefully: based on this evidence alone ? Parents A Parents B Infant Infant Father Mother Father Mother X Y ___________________________________________________________________ (-) __ __ __ __ __ __ __ __ __ __ __ __ __ (+) __________________________________________________________________ a) infant X is the child of Parents B b) Infant Y is the child of parents A c) One infant is the child of neither Parents A or B d) a and c apply e) b and c apply 42. To create a transgenic cow that would synthesize a human protein in milk, you would ? a) Inject total human DNA into the mammary gland b) Select embryonal stem cells (ES) transfected with a human gene under control of a promoter expressed in all somatic cells c) Select embryonal stem cells (ES) transfected with a human gene under control of a DNA sequence specific for proteins secreted in milk such as lactalbumin and transfer these cells to early blastulas d) None of the above 43. A cDNA library is prepared from muscle cells & liver cells. You expect the genes found in these two libraries to be? a) The same b) Partially overlapping c) Totally different 44. Hershey showed that when a bacteriophage was labeled with 32P (to label DNA) and 35S (to label protein) the production of new phage by E. coli resulted from ? a. The injection of 32P and 35S labeled material into E. coli b. The injection of 35S labeled material c. The injection of 32P labeled material 45. Single strand DNA binding protein is required to ? a. Identify the origin of replication b. Prevent base pairing in lagging strand Bil 255 Test # 2 – Glaser – Form 0 – pg 5 The following two questions (46 & 47) are related. 46. The following is the nucleotide sequence, starting with AUG for a normal cellular protein, and three mutant forms (a genetic code is attached at the end of the exam). start Normal __ AUGUUAAGAUUCAAA _ _ __ Mutant 1 __ AUGUGAAGAUUCAAA _ __ __ Mutant 2 __ AUGUUAAGGUUCAAA _ __ __ Mutant 3 __ AUGUUAAGGUUCCAN _ __ __ You examine the cells containing each of these mutations for presence of normal or mutant proteins and you find one of them has no measurable protein. This cell is ? a) Mutant 1 b) Mutant 2 c) Mutant 3 47. You examine these same cells to determine which has a fully functional protein. The choices are ? a) Mutant 1 b) Mutant 2 c) Mutant 3 d) None of these is correct 48. The sequence cleaved by the enzyme HaeIII is …………………………………………> --- GG __ CC--Using a probe for a portion of the sequence of the gene for Malterase, you obtain --- CC __ GG--the following results in normal and mutant live cells, after cleavage of the DNA, electrophoresis and assay with the probe. Normal Mutant DNA sequencing shows a single base change and a single amino acid has been changed in Malterase. Using the genetic code, can you distinguish ______ which of the following alternatives is possible ? a) Glycine – Arginine b) Proline – Isoleucine ______ c) Proline – Threonine 49. Many amino acids are specified by multiple code words often differing from each other at the third base, but in many cases differing in all three positions. The amino-acyl tRNA synthetase for the amino acid recognizes all of the tRNA’s that code for that amino acid. Would you conclude from this statement that ? a) This enzyme functions exclusively by recognizing the anticodon in the tRNA b) This enzyme at a minimum must recognize another feature of the tRNA in addition to the anticodon sequence. 50. You develop, in the laboratory, a new E. coli strain that has a CAP protein that binds to appropriate DNA sequence independent of the concentration of cAMP in the cells. You expect to see ß-galactosidase synthesis in these cells: a) Only when cells are grown without glucose b) Only when cells are grown in the presence of a beta-galactoside c) Both a and b must attain Bil 255 Test # 2 – Glaser – Form 0 – pg 6 SECOND LETTER U C UUU A UCU UAU UUC UUA F I R S TC UCC s er UAC cys UGC C UAA stop UGA stop A UUG UCG UAG stop UGG trp G CUU CCU CAU CUC l eu CCC pro CCA CAC CGU his CAA CUG CCG CAG AUU ACU ACC AAC AUC ile AUA ACA met val ACG AAG a sn ala GAC GUA GCA GCG GAG CGG G U AGC s er AGG GGC C A arg GGU a sp GAA GUG C G U gly C GGA glu T H I R D A AGA lys GAU GCC arg AGU AAA GCU GUU GUC thr CGC U CGA gln AAU AUG G U UCA l eu CUA L E T TA E R UGU tyr phe U G A GGG G L E T T E R ...
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