C.Multiple Choice Questions

Instructions: Select the single best answer to each of the questions given below. Each question is worth one mark, for a total of 30 marks.

5. Which of the following is NOT correct about bacterial conjugation? a. F– cells do not contain the F factor. b. Bacterial conjugation results in an exchange of genes between two bacterial cells. c. Genes on the F factor code for sex pili. d. Genes can be transferred from the donor to the recipient. e. Hfr cells can produce sex pili.

6. In generalized transduction, a bacterium obtains DNA from a virus as a result of a lytic cycle. The bacterium will a. survive. b. harbour a prophage. c. die immediately. d. reproduce for a few generations, until the prophage becomes virulent. e. contain virus nucleic acid.

 7. A repressible operon is usually controlled by a. an inactive repressor that allows the operon to be in the “on” state. b. the supply of the precursor product for the enzymes. c. an inactive repressor that keeps the operon in the “off” state. d. tryptophan. e. being turned “on,” usually by the end product of the pathway.

9. Translocation occurs when a. part of a chromosome breaks off and attaches to a nonhomologous chromosome. b. part of a chromosome breaks off and attaches to a homologous chromosome. c. crossing-over events occur. d. genes move from one area on a chromosome to another area on the same chromosome. e. a Y chromosome replaces an X chromosome in a female cell.

 10. In a plant cell, cytokinesis begins with the formation of a. an aster. b. a mitotic spindle. c. a Golgi complex. d. a cell wall. e. a cell plate.

11. In a human cell at prophase I, there are ________ tetrads. a. 92 b. 46 c. 23 d. 2 e. 4

15. Binary fission occurs when a. mitosis takes place without cytokinesis. b. homologous chromosomes have already paired. c. the cyclin-Cdk complex is no longer phosphorylating enzymes. d. the cell cycle is out of control. e. a prokaryotic cell reproduces.

 16. “Sticky ends” are a. the single-stranded ends of a DNA segment created by some restriction enzymes. b. a problem in recombinant DNA technology because they form loops of single-stranded DNA. c. double-stranded ends of a DNA segment created by some restriction enzymes. d. sites of the origin of replication in prokaryotes. e. sugar molecules that are bound to the ends of a DNA fragment. Principles of Biology I 7

 

22. Which of the following statements concerning the cell cycle is FALSE? a. CDKs are involved in the regulation of the cell cycle. b. External factors are involved in the regulation of the cell cycle. c. CDKs are active only when they bind to cyclins. d. The amount of CDKs changes during the cell cycle. e. Several types of cyclin regulate different phases of the cell cycle.

23. How does the first nucleotide at the 5’ end of a new mRNA chain differ from the other nucleotides in the chain? a. The first nucleotide is always a uracil. b. The first nucleotide is always a cytosine. c. The first nucleotide retains its triphosphate group, while the others do not. d. The first nucleotide does not retain its triphosphate group, while the others in the chain do. e. The first nucleotide is always a modified cytosine.

25. Why does DNA synthesis only proceed in the 5’ to 3’ direction? a. Because DNA polymerases can only add nucleotides to the 3’ end of a polynucleotide strand. b. Because the 3’ end of the polynucleotide molecule is more electronegative than the 5’ end. c. Because that is the direction in which the two strands of DNA unzip. d. Because that is the only direction that the polymerase can be oriented. e. Because the chromosomes are always aligned in the 5’ to 3’ direction in the nucleus. Principles of Biology I 9

27. Random segregation refers to a. crossing over. b. regulation of mitosis. c. events during transduction. d. Barr bodies. e. paternal and maternal chromosomes.

28. Where is the amino-acid binding site located on the tRNA molecule? a. in the middle of the loop b. at the 3’ end of the molecule c. in the first loop d. along the longest stretch of base pairing in the molecule e. at the 5’ end of the molecule

29. During mismatch repair of DNA, the repair enzyme a. will remove several nucleotides on both DNA strands. b. will remove several nucleotides on one DNA strand. c. will remove only the mismatched nucleotide. d. will remove the mismatched nucleotide, and the same enzyme will replace it with the correct nucleotide. e. is unable to detect mutations.

 

30. Which of the following is TRUE regarding alternative splicing? a. It is very uncommon in humans. b. One strand of DNA can produce different mRNAs. c. Introns are often absent. d. As a result, the same proteins are produced in different cell types. e. All exons are used to produce m-RNA. 

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