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AGR 3303 (3 credits) University of Florida - Fort Lauderdale  |
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| Below is exam #2 for 1996, Molecular genetics |
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AGR 3303 - Genetics 24 Oct 1996 University of Florida - Fort Lauderdale Exam #2: MOLECULAR GENETICS Student name_______________________________ Multiple choice (60 pts.) Please read these carefully. One and only one response (a, b, c, d, or e) completely and correctly answers the question, or completes the statement. Circle the appropriate response ON THE SEPARATE ANSWER SHEET and keep this exam. Make sure your circle is unambiguous. Take time to relax. 1. Which of the following is a nucleotide of DNA: a. deoxyribose + guanine + phosphate group b. deoxyribose + uracil + phosphate group c. ribose + pyrimidine + phosphate group d. deoxyribose + nitrogenous base e. none of the above 2. A gene has both a normal form and an abnormal form. The abnormal form of the gene produces an abnormal polypeptide, which disables the function of the resulting monomeric enzyme. Why would heterozygotes (individuals with a normal copy and an abnormal copy of the gene) be functionally normal? a. because normal polypeptides would join together 25% of the time b. because of the limited correction due to frameshift mutations c. because enzymes can be effective in partial amounts d. because of diffusible substances e. none of the above 3. Translation: a. involves highly repetitive DNA b. produces ribosomal rRNA c. produces polypeptide d. occurs in the nucleus e. produces tRNA 4. DNA is recovered from an orc, believed to be a fearsome species of goblin. The DNA contains the following composition of bases: adenine 16%, guanine 33%, thymine 17%, cytosine 34%. The orcs most likely have: a. double-stranded DNA b. double-stranded RNA c. single-stranded DNA d. single-stranded RNA e. a bad case of nausea following trick-or-treat 5. The Central Dogma examines which characteristic of the genetic material? a. replication b. mutation c. expression d. storage e. dominance 6. Watson and Crick (1953) proposed: a. the genetic code b. the double-helix model of DNA c. the polymerase chain reaction d. that DNA is the hereditary molecule e. the Central Dogma 7. Which statement is true of the double helix? a. heating causes the strands to denature b. GC pairs involve three hydrogen bonds c. purine pairs with pyrimidine d. all of the above e. none of the above 8. Human insulin can be produced by bacteria, using human DNA. This proves that: a. the genetic code is a heteropolymer specifying a single amino acid b. a new amino acid is transcribed from a nonsense mutation c. avirulent bacteria can be rendered infectious with exogenous DNA d. bacteria and humans must have similar coding dictionaries e. translation requires oligomeric proteins homologous to ribosomal tRNA 9. The human genetic disease phenylketonuria (PKU) can result in mental retardation, due to the accumulation of unmetabolized phenylpyruvic acid, which is a toxic byproduct of unmetabolized phenylalanine. PKU is caused by a homozygous recessive allele; heterozygous persons are normal. Diagnosis of PKU in newborns can help prevent retardation, by identifying infants who must be kept on a diet low in phenylalanine, thus reducing the accumulation of phenylpyruvic acid. This shows that: a. the phenotype is affected by the environment b. the normal gene specifies an oligomeric enzyme c. phenylpyruvic acid is a diffusible substance d. all of the above e. none of the above 10. Based on the Watson-Crick model of the double helix: a. for every purine there must be a pyrimidine b. if you know the content of one nitrogenous base (e.g., A) then you know the content of the other three (e.g., T, G, and C) c. nitrogenous bases of antiparallel strands are paired by hydrogen bonds d. the structure explains the function e. all of the above 11. A cell-free synthesizing system was used to translate the genetic code, using artificial RNA templates. RNA sequences in these templates were matched to amino acid(s), based on the retention of radioactively labelled amino acid. Which concept(s) would be reasonably help the deciphering effort. a. RNA homopolymers should code for more than one amino acid b. RNA heteropolymers could code for only one amino acid c. the ratio of nucleotides predicts the ratio of amino acids d. all of the above e. none of the above 12. DNA replication can lead to Okazaki fragments, if it is prematurely stopped, because: a. new DNA synthesis occurs in the 5'-3' direction on one strand, and 3'-5' on the other strand b. DNA synthesis is semiconservative c. DNA synthesis takes place in the nucleus, while protein synthesis occurs in the cytoplasm d. all of the above e. none of the above 13. What has molecular biology added to the knowledge of genetics a. proof that genes act as particles b. proof that genes are made of chemicals c. proof that genes are located in the chromosomes d. proof of the inheritance of acquired characteristics e. proof that both the female and the male parent contribute to the characteristics of the offspring 14. The bacteria of Avery et al. (1944) were transformed by a substance which as inactivated by: a. RNase b. DNase c. 32P d. 35S e. none of the above 15. In a galaxy far, far away, aliens are discovered. Their genetic material is double-stranded DNA, with the same nitrogenous bases (A, T, G, and C) as earth-based DNA. The aliens' genetic code is based on a linear sequence of codons, with no overlap, just like on earth. However, in contrast to earth-based molecular biology, the code is based on a doublet reading frame (i.e., two nucleotides per codon). Therefore: a. the aliens must have more nonsense codons than earthlings b. the aliens must have fewer amino acids than earthlings c. the aliens must have more amino acids than earthlings d. the aliens must have 24 amino acids e. any one of the above is possible 16. The Hershey-Chase experiment infected bacteria with radioactively labelled phage virus, proving that DNA, not protein, was the genetic material, because: a. radioactive P was found in the infected bacteria, and radioactive S was found in the phage "ghosts" (the remaining protein coats) b. both radioactive P and S were found in the infected bacteria c. radioactive S was found in the infected bacteria, and radioactive P was found in the phage "ghosts" (the remaining protein coats) d. both radioactive P and S were associated with the phage "ghosts" (the remaining protein coats) e. none of the above 17. Polynucleotides: a. are polymers b. contain P, not S c. are present in the nucleus d. are present in the mitochondria e. all of the above 18. Parent plants with the genotypes AABBCC and aabbcc were crossed, and their F1 progeny were backcrossed to a homozygous recessive tester. The 1000 backcross progeny had the phenotypic distribution: Phenotype ABC abc AbC aBc Abc aBC ABc abC Number 355 355 5 5 95 95 45 45 What is the map distance between A and C? a. 1 map unit b. 10 map units c. 20 map units d. 30 map units e. 40 map units 19. What molecule is transcribed from the DNA template, is single stranded, is typically a large molecule, and has a short half-life (high turnover)? a. mRNA b. tRNA c. rRNA d. all of the above e. none of the above 20. In replication, each double-stranded daughter DNA is composed of one strand which is old and one which is newly synthesized, thus replication: a. is collinear b. is conservative c. is complementary d. all of the above e. none of the above True or false? (15 pts.) Each statement is either true or false. Please circle T for true or F for false ON THE SEPARATE ANSWER SHEET 21. T F DNA polymerase is active in translation. 22. T F Restriction enzymes are the cornerstone of recombinant DNA technology. 23. T F A polypeptide is a large molecule made up of nucleic acids. 24. T F The Central Dogma deals with replication. 25. T F Retroviruses are RNA viruses which use RNA polymerase to make a DNA "copy" of their RNA. 26. T F It is possible to amplify dinosaur DNA. 27. T F Mitochondria may be ancient cell invaders. 28. T F A gene can be defined as a chemical factor of inheritance. 29. T F Linkage is consistent with the idea that genes are carried on chromosomes 30. T F Heterochromatin constitutes genetically turned on chromosome regions. 31. T F Prokaryotic gene regulation involves simultaneous transcription and translation. 32. T F If the single-stranded DNA sequence is 5' GGC 3', then the mRNA sequence is 5' CCG 3'. 33. T F In replication, the daughter DNA is composed of two new strands. 34. T F A synthetic mRNA heteropolymer made of two nucleic acids can translate more than two amino acids. 35. T F The ribosomes are active in transcription.
Matching (10 pts.) ON THE SEPARATE ANSWER SHEET, insert the correct word or phrase from the list at the bottom of the page. 36. "Wobble" in the third nucleotide of tRNA's anticodon is believed to result in inexact complementarity. This permits what key characteristic of the genetic code?
__________________________________.
37. A labelled macromolecule, such as DNA, which is used to detect target molecules
__________________________________.
38. A type of protein made of two or more polypeptides
__________________________________.
39. A type of mutation involving a deletion or an insertion of one or more nucleotides, resulting in a garbled message
__________________________________. 40. The correspondence between the sequence of nucleotides and the sequence of amino acids resulting from translation
__________________________________. 41. A cutter enzyme
__________________________________. 42. A protein present in the eukaryotic chromosome
__________________________________. 43. The place in a protein where structural integrity is required for function; mutations which disrupt the protein here usually result in defective protein
__________________________________. 44. A method for amplifying DNA segments to large number of copies
__________________________________. 45. The three-nucleotide decoding sequence used by tRNA
__________________________________.
Short answer PLEASE USE THE SEPARATE ANSWER SHEET (15 pts.) 46. Mutations occur with varying expressions in the organism; here are some examples. Imagine that different point mutations (nucleotide substitutions) occur in a structural gene (one which contains the message for a polypeptide). Please explain why the different expressions might arise. (8 pts.)
47. In what three genetic processes is complementarity important? (3 pts.)
48. What are the four characteristics of the hereditary material? (4 pts.) |
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