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Biology 141 – General Biology Fall 2013 – Dr. Carey – Exam 4 Name______________________________ Part I – Multiple Choice – 1 pt. each. 1. How many mRNA codons are necessary to produce a protein containing 120 amino acids? A) 40 B) 60 C) 120 D) 240 E) 360 2. How many DNA bases are necessary to produce a protein containing 120 amino acids? _______ (Use the choices in question 1) 3. How many tRNA molecules are necessary to produce a protein containing 120 amino acids? _______ (Use the choices in question 1) 4. Hershey and Chase labeled viruses with radioactive P and S. Their results led to the conclusion that: A) the nucleus controls the cell B) one gene codes for one enzyme C) the genetic material is protein D) enzymes are proteins E) the genetic material is DNA 5. Free nucleotides can be attached to a growing nucleic acid chain: A) at either end B) at any point in the chain C) only in ribosomes D) only at the 5’ end E) only at the 3’ end 6. A certain section of DNA has the base sequence AGCCTATAG. The complementary sequence formed during transcription is: A) TCGGATATC B) AGCCTATAG C) UCGGAUAUC D) AGCCUAUAG E) TCGGUTUTC 7. Using the choices in question 6, what would be the complimentary sequence formed during replication? ________ 8. To begin the process of translation, mRNA will first bind with: A) a large ribosome subunit B) an appropriate tRNA C) a DNA transcript D) a small ribosome subunit E) RNA polymerase 9. We have a codon with the base sequence CGA. The DNA sequence that produced it was: A) CGA B) GCT C) CGU D) GCU E) CGT 10. Corepressors are molecules that: A) attach to operators B) attach to promoters C) activate repressors D) inactivate repressors E) slow down rates of translation 11. Operon theory is a well supported theory for transcription control in: A) humans B) prokaryotic cells C) lower animals D) plants E) more than one of the above 12. Which of the following does not contain base codes that could be used in the production of a protein? A) operator B) structural gene C) cistron D) operon E) exon 13. If 20% of the nucleotides in a DNA molecule are adenosine, what percent are cytosine? A) 20 B) 30 C) 40 D) 60 E) 80 F) there is not enough information to answer the question 14. If 20% of the nucleotides in an RNA molecule are adenosine, what percent are cytosine? ______ (Use the choices in question 13) 15. In a DNA molecule, guanine binds to its normal complementary base with ____ hydrogen bonds. A) 1 B) 2 C) 3 D) 4 E) 5 16. All else being equal, the most efficient method of controlling gene expression would be to control: A) replication B) translation C) transcription D) protein function E) RNA production F) none of the above 17. In controlling gene expression, which mechanism is not used by prokaryotes? ________ (Use the choices in question 16) Part II – Fill-in – 1 pt. each bank. 1. ____________________________ was the person who discovered that pairs of DNA bases come in equal concentrations. Prior to this discovery it was thought that all 4 bases had equal concentrations. This earlier data led many to believe that, chemically, genes were _____________________ in nature, because only this substance seemed to possess the necessary ___________________ in structure to be able influence all the different characters in living things. 2. Of the 64 codons possible, ___________________ of them are called stop codons. Which amino acid do these stop codons specify? _________________. Of the 64, _______________________ codon(s) is(are) start codons. Which amino acid is specified by a start codon? ___________________________. 3. To keep the two chains of a DNA molecule parallel, one large ____________________ base must be paired with one small ____________________ base across the middle. This large base/small base pairing occurs normally in DNA, but also occurs with a point mutation type known as a(n) ________________________. Actually the 2 chains of DNA are more appropriately described as ____________________ to each other, because, though they are parallel, they are opposite in ____________________________. Part III – True-false – 1 pt. each. 1. A point mutation will cause at least one amino acid change in the protein it codes for. 2. The structure drawn at right could be a schematic representation of uracil. 3. A frameshift mutation could potentially change all of the amino acids in a protein. 4. DNA is replicated in a conservative manner. 5. In order for a eukaryotic messenger to be translated, the exons must first be removed from it. 6. A single codon may specify more than one amino acid. 8. A single amino acid may be specified by more than one codon. 9. It is possible for 70% of the nucleotides in a DNA molecule to be cytosine. 10. It is possible for 70% of the nucleotides in an RNA molecule to be cytosine. Part IV – Short answer – pts as indicated. 1. Define: (3 pts each) A. regulator gene B. translocation C. codon D. Okazaki fragment E. “A” site on a ribosome F. frameshift mutation 2. Describe Griffith’s work that led him to the notion of bacterial transformation. (13 pts) 3. Draw and label an operon containing all 3 possible functional regions. Describe the function of each part. (12 pts) 4. Draw a representation of a tRNA molecule. Give the function of each major binding site on it. (10 pts) 5. List 3 chemical or structural differences between RNA and DNA. (9 pts)