ZOOL/BOT 3333

The answers to the practice exam are found here, but please work the practice exam first!

A. True/False and multiple choice questions (2 points each). Please fill in your answers on the scantron sheets provided. For true/false questions, please indicate whether a statement is true (1) or false (2), or, for multiple choice questions, circle the letter representing the single best choice. If a question seems ambiguous to you, please raise your hand and I will try to clarify the source of ambiguity.

1. Chromosome telomeres:
   a) are found at the ends of eukaryotic chromosomes; b) contain tandem arrays of a simple repeated sequence; c) have a common structural organization which is conserved among eukaryotes; d) all of the above; e) none of the above.
2. Reverse transcriptase:
   a) produces mRNA from viral DNA; b) is located strictly in the nucleolus; c) polymerizes RNA in a 3' to 5' direction; c) is an RNA dependent DNA polymerase; e) none of the above.
3. The members of the human globin gene family:
   a) are all expressed at the same time during development; b) synthesize proteins with identical physiological properties; c) are located on the same chromosome; d) all of the above; e) none of the above.
4. True or false. For any given tissue, the chromatin structure of genes that are actively being transcribed is indistinguishable from the chromatin structure of genes that are not being transcribed.
5. Mitochondrial DNA:
   a) is circular; b) contains its own genes for ribosomal RNA; c) differs in size depending on the organism; d) all of the above; e) none of the above.
6. Suppose DNA had evolved to include only the bases adenine and thymine. Assuming the current number of amino acids were involved in the synthesis of proteins, how long would a code word have to be to have at least 1 unique code word for each amino acid?
   a) 2 bases; b) 3 bases; c) 4 bases; d) 5 bases; e) 6 bases.
7. tRNA molecules:
   a) can carry an amino acid at their 3' ends; b) contain two anti-parallel strands of RNA in a cloverleaf structure; c) contain thymine instead of uracil; d) all of the above; e) none of the above.

Questions 8-10 pertain to the following diagram:

8. This diagram represents:
   a) mRNA synthesis in a prokaryote; b) mRNA synthesis in a eukaryote; c) mRNA synthesis in either a prokaryote or a eukaryote, since the process of transcription is essentially universal.
9. The molecule indicated as "A" in the above figure:
   a) is the enzyme also used to synthesize ribosomal RNA; b) will terminate transcription at the Shine-Dalgarno sequence; c) began the process of transcription by binding to a promoter; d) all of the above; e) none of the above.
10. True or false. The molecule indicated as "B" in the figure represents a ribosome entering to begin the process of translation.
11. True or false. Proteins are the only macromolecules which perform an enzymatic (catalytic) function in biological reactions.
12. If the synthetic nucleotide 5'-(GCA)_n-3' were added to the synthetic in vitro protein synthesizing system of Khorana, what polypeptides would be synthesized in the reaction?
    a) (Ala-Gln-Ser)_n; b) (Arg-Val-Ser)_n; c) (Ala-Ala)_n + (Gln-Gln)_n + (Ser-Ser)_n; d) (Thr-Thr)_n + (Arg-Arg)_n + (Asp-Asp)_n; e) (Thr-Arg-Asp)_n
13. True or false. The redundant nature of the genetic code leads to a requirement for 61 different tRNA molecules.
14. An enzyme that has tertiary structure, but not quaternary structure, is coded for by how many cistrons?
    a) 1; b) 2; c) 3; d) 4; e) 5.
15. True or false. The fine structure mapping experiments on the T4 rII locus to demonstrated that within genes, all sites appear to be equally susceptible to mutation.

Questions 16-17 pertain to the following:

strain number      	precursors added to minimal medium
			A	B	C	D	E	Z
1			-	+	+	+	+	+             

2			-	-	-	-	-	+

3 			-	+	-	-	-	+

4			-	+	_	+	+	+              

5 			-	+	-	-	+	+

16. From the above data, the biochemical pathway leading to Z is:
    a) A>B>E>D>C>Z; b) A>C>D>E>B>Z; c) C>A>B>E>D>Z; d) E>B>C>A>D>Z; e) none of the above.
17. From the above data, the gene locus encoding the enzyme responsible for producing compound D is mutant in strain:
    a) 1; b) 2; c) 3; d) 4; e) 5.
18. In experiments using repeating polymers, (GCGC)_nincorporates alanine and arginine into peptides, and (CGGCGG)_n incorporates arginine, glycine and alanine. On On the basis of this experiment, what codon can definitely be assigned to glycine?
    a) GCG; b) CGC; c) GGC; d) GGG; e) GCC.
19. True or false. It is the tRNA, not the amino acid attached to it, that is recognized at the ribosome during the process of translation.
20. The formation of which covalent linkage is catalyzed by the large ribosomal subunit?
    a) James Bond; b) Ward Bond; c) Julian Bond; d) U.S. Bonds; e) peptide bond.

B. Match and Identify (2 points each). Please match the following terms in part I with the appropriate definitions, characteristics or specific examples given in part II. For each term, provide the single best answer; no term in part II should be used more than once. Please note that two circles must be filled for each answer.

part I.

21-2. AUG codon
23-4. polycistronic mRNA
25-6. SnRNP
27-8. inosine
29-30. frameshift mutation
31-2. 7-methyl guanosine
33-4. sigma factor
34-5. TATA box
37-8. trinucleotide binding assay
39-40. characteristic of mitochondrial chromosome

part II.

aa) feature of eukaryotic mRNA
bb) induced by proflavin dyes
cc) part of E. coli RNA polymerase holoenzyme
dd) product of operon transcription
ee) DNA binding site for RNA polymerase
ab) component of spliceosome
ac) Shine-Dalgarno sequence
ad) used to decipher genetic code
ae) nucleotide found in tRNA anticodons
ba) start signal for translation
bc) telomeres
bd) demonstrated that the genetic code is truly universal
be) termination codon
ca) cytoplasmic inheritance

C. Short Problems (15 points). Please answer the following problems. Be sure to show all work (eg. calculations); partial credit can only be assigned on the basis of work shown.

1. Each of six mutant strains of a little-studied bacteriophage show the same phenotype. Research indicates that the mutation carried by each of these strains is located in the same general region of the viral chromosome. A series of pairwise matings between these six mutant types is carried out using an appropriate restrictive bacterial host. The outcome of each mating is summarized in the following chart, where a plus sign (+) indicates the production of progeny phages and a minus sign (-) indicates no phage produced.

                         
MUTANTS        1    2    3    4    5    6
  
  1            -    +    +    +    +    +

  2                 -    +    +    -    + 

  3                      -    -    +    -

  4                           -    +    -

  5                                -    +

  6                                     -

a) From the above data, who many different gene loci appear to be located in this region of the phage chromosome?
b) From the above data, which mutations appear to be located in the same gene?

2. (8 points). Some codons in the genetic code were determined by the translation of random polymers. If a ribonucleotide is synthesized that contains 3/4 G and 1/4 C in random order, which amino acids would the resulting peptide contain, and in what frequencies?

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