Question

1. An enzyme used to covalently join DNA segments to form recombinant DNA molecules is called a A. Restriction endonuclease B. Reverse transcriptase C. DNA polymerase D. Helicase E. Ligase 7. The procedure for introducing changes into specific genes is called A. An enhancer trap B. Imprinting C. RT-PCR D. DNA looping E. Gene targeting 2. Plasmids used for in vitro cloning of foreign DNA fragments are called A. Donors B. DNA chips C. Clones D. Vectors E. Conjugants 8. When interpreting the results of microarrays, the degree of hybridization between a given probe and an organism to be identified is measured by A. Turbidity read in a spectrophotometer B. Color intensity of the slide image produced by scanning it with a laser beam C. Length of the probe formed D. Degree of agglutination E. Microscopy 3. What kind of termini is produced by the restriction endonuclease Pxul, which restriction site has is 5'-CGAT C-3'? (The downward arrow represents the site of cleavage in each strand.) A. 3' overhang B. 5' overhang C. Blunt ends D. Reverse ends E. Polvlinker termini 9. Which of the following is NOT a necessary feature of a good cloning vector? A. The ability to carry DNA fragments from 5 kb up to 200 kb B. The ability to be replicated C. Restriction site(s) for the insertion of a foreign DNA fragment D. A selectable marker gene E. The ability to be isolated from the host cell 4. Enzyme that cleave DNA at sequence-specific sites is called A. DNA polymerase B. Ligase C. Restriction endonuclease D. Exonuclease E. Integrase 10. In gene-targeting experiments, the replacement of the wild-type gene in the genome with the completely unfunctional gene results in an) A. Knockout mutation B. Imprinting C. Transformation rescue D. Conditional mutation E. Forward mutation 5. The technique to look for possible gene function by mutating wild-type genes is called A. Gene therapy B. Reverse genetics C. Transgenetics D. Contig building E. Gene mapping 11. The ability of an introduced DNA fragment to correct a genetic defect in a mutant organism is called A. An insertional inactivation B. A transformation rescue C. An enhancer trap D. A mismatch repair E. Gene targeting 6. Which of the following vectors can accept the largest DNA fragments in cloning experiments? A. Plasmid D. Cosmids B. Bacteriophage lambda E. Phage P1 C. BACs 12. What is the reaction catalyzed by the enzyme reverse transcriptase? A. Synthesis of DNA from a single-stranded RNA molecule B. Synthesis of RNA from a DNA template C. Circularization of restriction fragments D. Cleavage of DNA at a sequence-specific site E. Ligation of DNA fragments

Answer 1

1. E) Ligase catalyzes the joining of two terminals of DNA.

2. D) Vectors includes plasmids, bacterial artifical chromosome (BAC), yeast artificial chromosome (YAC), phage DNA and cosmids.

3. A) 3' overhang because cleaved single-stranded bases end with a 3' hydroxyl.

4. C) Restriction endonuclease recognize a specific palindromic sequence and cleaves it.

5. B) Reverse genetics. It starts from a protein/DNA with unknown function and then works backward to make a mutant gene, resulting in mutant phenotype.

6. C) BACs have the highest capacity (150-350 kbp) out of the given Vectors: plasmid (5 kbp), cosmid (35-45 kbp), bacteriophage lambda (35-50 kbp), phage p1 (75-100 kbp).