Test 2 Spring 2000

Test 2 Spring 2000 - Bil 255 Spring 2000 Charles Mallery...

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Unformatted text preview: Bil 255 Spring 2000 Charles Mallery Test # 2 April 05, 2000 FORM 0 Directions: 1 hour 15 minutes – 100 points. From among the choices for each question, PICK the BEST choice . 1. 2. DNA synthesis is always initiated by : a) An RNA primer b) A guanosine cap c) A deoxyribonucleotide triphosphate The following proteins are required for DNA synthesis : a) DNA polymerase, primase, sliding clamp c) RNA polymerase d) a and b apply b) Helicase, DNA ligase e) b and c apply 3. 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 4. RNA is synthesized by copying DNA : a) Both strands of DNA are transcribed to yield double stranded RNA b) At any position in the genome only one strand of DNA is transcribed 5. Messenger RNA’s differ in procaryotes and eucaryotes : a) Procaryotic messages are polycistronic (code for more than one protein) and eucaryotic messages only code for one protein b) Procaryotic messages code for one protein, eucaryotic messages code for multiple proteins 6. Eucaryotic messenger 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 7. The junction 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 8. 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 9. The initiation of protein synthesis involves initially : a) The large subunit of ribosomes b) Small subunit of ribosomes c) Both 10. 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 11. A given messenger at any time will have attached to it :0 a) One ribosome at the end b) One ribosome at each end c) Multiple ribosomes in the process of synthesizing protein 12. In general the DNA in each cell of the body of a eucaryotic organism, for example man, : a) Is different in each cell type b) Is the same in each cell type 13. In eucaryotic cells all RNA molecules are : a) Made by the same RNA polymerase b) Made by different RNA polymerases Page 2 Form 0 Bil255s00 – Test #2 14. 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 15. 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 the concentration of specific ligands in cells, for example, an amino acid c) Are a component of RNA polymerase any 16. A given regulatory protein may : a) Control expression of a single gene b) Can control expression of multiple genes 17. The statement, "The expression of each gene is controlled by the sum of the positive and negative regulatory proteins that affect this gene," is : a) Correct b) False any 18. You chemically link the amino acid alanine (Ala) labeled with 14C to tRNA for leucine. You use this molecule in an in vitro system to synthesize a protein using appropriate mRNA, ribosomes, etc. The initial coding sequence for this protein is : 1 2 3 4 5 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 19. Higher organisms often contain multiple proteins which have apparently evolved from a common ancestral gene. The most likely origin of these is (for example, hemoglobin) : a) Unequal crossing over b) Bacterial infections c) Insertion of enhancer molecules close to the initiation site of gene transcription 20. Retroviruses contribute to genetic diversity because (think carefully, 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 21. Restriction enzymes cleave DNA : a) At random sites b) At unique sequences d) a and c apply e) b and c apply 22. c) The sequence at the site is often a palindrome The dideoxynucleotide method for sequencing DNA is based on : a) Chain termination of DNA polymerase action after a dideoxynucleotide is incorporated into DNA b) The separation of DNA molecules that differ in length by one nucleotide c) The knowledge of DNA sequence to synthesize a primer d) a and b apply e) a, b and c apply 23. When two cells are fused, after a short period of time you expect : a) All cell surface membrane proteins to be randomly distributed b) Some membrane proteins will not be able to diffuse in the plane of the membrane Page 3 Form 0 Bil255s00 – Test #2 NOTE Questions 24 - 26 are related 24. 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 probe to your clones at : a) High stringency b) Low stringency c) It does not matter, either will work 25. 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 : a) The pattern to be totally different b) The pattern of cleavage of baboon and human genes to be more similar than mouse and human c) The pattern of cleavage of baboon and human genes to be as different from each other as mouse and human 26. You completely sequence the hexokinase genes from all species and you compare the sequence 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 27. You wish to clone 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 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 28. Cellular membranes are best described as : a) Lipid bilayers that separate two aqueous compartments b) A fluid lipid bilayer containing multiple lipids and proteins c) A hydrophobic environment which allows proteins to move d) All apply 29. Tight junctions : a) Promote movement of proteins in membranes b) Restrict movement of proteins in membranes 30. For all cells is : a) Na+ inside > Na + outside 31. The concentration of amino acids in liver cells is generally higher than in extra-cellular fluid. In the presence of ouabain which inhibits Na +/K+ ATPase you expect to find for the amino acid alanine (Ala) : a) Ala i nside < Ala outside b) Ala inside > Ala outside b) Na+ outside > Na+ inside Page 4 Form 0 Bil255s00 – Test #2 32. 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 extra-cellular 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 co-transporter (symport) 33. In a cell under physiological conditions activation of the Na +/H+ antiport will : a) Increase cellular pH (i.e., cell becomes alkaline) b) Decrease cellular pH (i.e., cell becomes more acid) c) The question cannot be answered 34. DNA Ligase requires : a) An RNA primer b) ATP 35. A cDNA library from liver compared to muscle will : a) Consist of totally different DNA sequences b) Some common sequences and some different sequences 36. Which of the following statements is correct for eucaryotic cells? a) All cellular proteins are degraded at the same rate b) Each cellular protein is degraded at a different rate c) All proteins are degraded in lysosomes d) Some proteins are degraded in lysosomes, others in proteosomes e) b and d are correct 37. When the ribosome reaches a code word UGA, it : a) Releases the nascent protein still linked to tRNA b) Releases the nascent protein without tRNA c) Binds a release factor which allows peptidyl-transferase to release the protein d) a and c apply e) b and c apply 38. Consult the following restriction fragment length polymorphism detailed by hybridization to a DNA probe after digestion of human DNA with a restriction enzyme : Parents A Parents B Infant Infant Father Mother Father Mother X Y __________________________________________________________________ (__) __ __ __ __ __ __ __ __ __ __ __ __ __ (+) __________________________________________________________________ Think carefully, based on this evidence alone : 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 Page 5 39. Form 0 Bil255s00 – Test #2 The fluidity of membranes is an important physical property for survival of cells. Which of the following statements are correct? a) Procaryotes control membrane fluidity primarily by changing cholesterol content of the membrane and eucaryotes by changing the percentage of unsaturated fatty acids b) The reverse is true c) None of these statements apply NOTE Questions 40 and 41 are related 40. 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 ___ AUG UUAAGAUUCAAA _ _ __ __ _ __ __ 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 41. 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 42. Starting at an origin of replication, there are two replication forks moving away from the origin in opposite directions. Think carefully. a) The leading strand copies the same DNA strand in both forks b) Copies opposite DNA strands in the two forks 43. DNA synthesis is started with an RNA primer. Failure to make this RNA primer with high-fidelity will : a) Cause mutations b) Have no effect on cells c) Result in new mRNA’s 44. Bacterial mRNA’s are often polycistronic (i.e., code for multiple proteins). You expect these proteins to be : a) A random collection of proteins b) Proteins in a specific metabolic pathway 45. 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 in mating experiments 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 46. By careful breakage of cells, it is possible to isolate sealed vesicles (like liposomes) derived from the cytoplasmic membrane. You wish to determine whether these vesicles are oriented in the same way as the cytoplasmic membrane’s right side and/or in the inverted form, right side in. Lectins are proteins that bind to carbohydrates such as those present in the cytoplasmic membrane. You expect the lectin to bind to these vesicles if : a) They are right side out b) They are right side in Page 6 47. Form 0 Bil255s00 – Test #2 You need to clone in E. coli the gene for a small human enzyme for which you have a partial sequence. To do this you synthesize a fluorescent probe complementary to that sequence and use the following plasmid as a potential cloning vehicle. You cleave human DNA with the restriction enzyme glaserase and insert the DNA fragments in the plasmid with which you transfect an E. coli strain sensitive to tetracycline and unable to make ßgalactosidase. You also have available a substrate for ß-galactosidase which will turn bacterial colonies blue if they have this enzyme. In order to focus your efforts you would after transfection : a) Plate the E. coli on agar plates and use your probe to examine all colonies b) Plate only E. coli which can grow in the presence of tetracycline before using your probe c) Follow the protocol in b but only test colonies that lack ß-galactosidase 48. The polymerase chain reaction requires the following components : a) Deoxyribonucleoside triphosphates, DNA polymerase b) A primer oligonucleotide and DNA ligase c) Two different primer oligonucleotides d) a and b apply e) a and c apply 49. As a result of a mutation, you find a strain of mice who die rapidly at birth unless you feed them intravenously. They appear to die because they cannot take up glucose efficiently from the intestine. You are tired of feeding the mice intravenously and get sloppy. One of the mice gets loose while you are having breakfast causing you to spill salt and your cereal on the floor. The mouse eats these, runs away and is still doing okay by evening. You are puzzled, started feeding the mouse lots of NaCl (salt) and glucose and a miracle takes place. The mouse and all of its relative do well. Your hypothesis of the genetic defect in the mouse is a) A Glucose/Na+ symport in the intestine with low affinity for glucose b) A Glucose/Na+ symport in the intestine with low affinity for Na+ c) The intestine epithelial cells have a very high level of Na+/K + ATPase d) c and c apply e) b and c apply 50. I spent my whole spring break reading Essentials of Cell Biology and expect 100 points on this exam. a) Yes b) No either ...
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