Multiple Choice Questions on Restriction enzymes

restriction endonuclease
E coR1: Restriction Endonuclease
1. Which of the following is the most important discovery that leads to the development of rDNA (recombinant DNA) technology
a) discovery of double helix model by Watson and crick
b) Discovery of DNA as genetic material
c) discovery of restriction enzymes
d) all of these

2. Who discovered restriction enzymes
a) Watson and Crick
b) Jacob and Monad
c) Nathan, Arber and Smith
d) Boyer and Cohen

3. Restriction enzymes are enzymes
a) capable of cutting DNA molecule
b) capable of adding nucleotides to the 3’OH end
c) capable of restricting protein synthesise
d) capable of joining DNA molecules

4. Restriction enzymes capable of making internal cuts in a DNA molecule is called
a) restriction exonuclease
b) restriction endonuclesae
c) both a and b
d) S1 nuclease

5. Restriction enzymes are also called
a) molecular knives
b) molecular scissors
c) molecular scalpels
d) all of these

6. The sequence recognised by the restriction enzyme to cut the DNA is called
a) recognition site
b) restriction site
c) both a and b
d) cleavage sites

7.Which of the following are true regarding restriction enzyme
a) restriction enzyme are used to cut DNA molecule
b) restriction enzyme are used to construct restriction maps
c) restriction enzyme are used in RFLP
d) all of these

8. The type of restriction enzymes used in rDNA technology is
a) Type I
b) Type II
c) Type III
d) all of these

9. Which of the following statements are true regarding restriction enzymes
a) Type I and II enzymes cuts far away from the restriction sites
b) Type II cuts DNA within restriction sites
c) Eco R1 is a Type II restriction enzyme
d) all of these

10. Restriction sites of type II enzymes
a) generally are palindromic sequences
b) consists of 4-6 bp
c) mostly are palindromes with rotational symmetry
d) all of these

11.Single stranded unpaired extensions formed by restriction enzyme upon cleavage is called as
a) blunt ends
b) flush ends
c) sticky ends
d) none of these

12. Which of the following ions are required for the activity of Type II restriction enzymes
a) Ca2+
b) Mg2+
c) Cl2+
d) Mn2+

13. Restriction enzymes
a) are present in bacteria and are involved in host restriction system
b) cleave viral DNA inside bacterium
c) are enzymes involved in defence against bacteriophages
d) all of these

14. Nathen, Arber and Smith were awarded with Nobel prize for physiology and medicine in the year
a) 1970
b) 1974
c) 1978
d) 1980

15. The first Type II enzyme isolated was
a) Eco R1
b) Hind III
c) Bam HI
d) Sal I

16. Which of the following are the characteristics of Type II restriction endonucleases? 

 1. Bifunctional enzyme with both endonuclease and methylase activity 

 2. Contains two identical subunits 

 3. Restriction requires ATP and Mg2+ 

 4. Cleavage site is at or near restriction site 

a) 1 & 2 only

b) 2 & 4 only 

c) 1 & 4 only 

d) 3 & 4 only 

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1. c) discovery of restriction enzymes
2. c) Nathan, Arber and Smith
3. a) capable of cutting DNA molecule
4. b) restriction endonuclesae
5. d) all of these
6. c) both a and b
7. d) all of these
8. b) Type II
9. d) all of these
10.d) all of these
11.c) sticky ends
12.b) Mg2+
13. d) all of these
14. c) 1978
15. b) Hind III
16. b)2 & 4 only
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