Agr 3303 Exam 2

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  • Topic: RNA, DNA, Gene expression
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AGR 3303 Genetics Exam 2 February 28, 2007
There are 25 questions and each correct response is worth 4 points. Please darken in the circles to spell your last name, FI, and MI and to record your UF ID and test code number. The test code number is located at the bottom of each page of your exam and should be recorded in the spaces provided for questions 76-80. Failure to correctly mark your the test code will result in a grade of 0 for your exam score. Once exams have been graded, your grade will be available through the class website ("exam grades" link). You will need your test code number to access your grade so keep your copy of the exam. Be sure to use a #2 pencil to mark the grade sheet or the computer will not be able to properly grade your exam. Make sure you densely mark the circle corresponding to your choice and make all erasures complete. When you have completed your exam, turn in your scan sheet at the front of the room. 1. The primary structure of a protein represents: (*) the amino acid sequence. (2) the functional configuration. (3) the subunits of a protein. (4) a pleated sheet. (5) a alpha helix. 2. In prokaryotes, most genes are organized into operons. One component of an operon is the structural genes. Which of the following best describes a structural gene? (*) a sequence of DNA that specifies a polypeptide. (2) a sequence of DNA that produces tRNA's. (3) a sequence of DNA that interacts with the small ribosomal subunit. (4) a sequence of DNA that is recognized by RNA polymerase. (5) a sequence of DNA that is involved in forming the structure of a double helix molecule. 3. Identify the correct sequence of steps in protein synthesis in prokaryotes: A - binding of large ribosomal subunit to initiation complex B - peptide bond formation C - binding of mRNA to small subunit of ribosome D - binding of charged tRNA to A site E - release of fmet-tRNA and translocation (1) B, C, A, D, E (2) B, E, C, A, D (3) C, E, B, A, D (*) C, A, D, B, E (5) C, D, A, B, E

4. What is the function of peptidyl transferase? (1) it charges tRNAs. (2) it acetylates the end of a protein after translation. (3) it cleaves the polypeptide from the last tRNA during termination. (4) it moves ribosomes along mRNA during translation. (*) it produces peptide bonds. 5. The most important difference between an intron and an exon is that: (1) only the introns are transcribed. (2) both types of sequences are transcribed and translated. (*) only the exons are translated. (4) both types of sequences are transcribed but neither is translated. (5) introns occur in prokaryotes, whereas exons occur in eukaryotes. 6. The genetic code is said to be degenerate and unambiguous. Which of the following is correct with regard to these descriptions? (1) it is unambiguous because three consecutive triplets specify one amino acid. (*) it is degenerate because more than one triplet codes for the same amino acid. (3) it is unambiguous because one triplet specifies more than one amino acid. (4) it is degenerate because the code has changed radically during evolution. (5) it is unambiguous because more than one tRNA can bond to the same codon. 7. An E. coli strain was found that had a mutation in the aminoacyl synthetase enzyme that charges the tRNA for formyl methionine (fmet). Instead of bonding a met to the tRNA, the enzyme attached an alanine instead. What effect would this have on protein (polypeptide) synthesis in this E. coli? (1) no protein synthesis would take place. (2) fmet would be the first amino acid in the polypeptide. (3) the polypeptide would have twice as much alanine as other polypeptides. (4) because of the wobble hypothesis, alanine would only replace met in some cases but not all. (*) the polypeptide would not contain any met. 8. If the template DNA sequence is 5'GACTGT, which of the following represents the transcription sequence? (*) 5'ACAGUC (2) 5'UGUCAG (3) 5'ACAGTC (4) 5'ACUGUC (5) 5'ACAGUG 9. Where would you find the repressor...
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