MCQ-3

11.Gel electrophoresis is used for

         a)   Construction of recombinant DNA by joining with cloning vectors

         b)   Isolation of DNA molecules

         c)   Cutting of DNA into fragments

     d) Separation of DNA fragments according to their size

12. Plasmids are extrachromosomal circular DNA molecules

a)  Which have their own point of replication and can replicate independently

b)  Which have their own point of replication and cannot replicate independently

c)  Which do not have on point of replication and cannot replicate independent of bacterial chromosome DNA.

d)  None of these

13. Recombinant DNA is achieved by cleaving the pro-DNAs by which of the following enzyme?

a)  Legase

b)  Primase

c)  Exonucleases

d)  Restriction endonuclease

14. Amplification of gene of interest by using DNA polymerase may go up to

a)  0.1 million times

b)  1.0 million times

c)  1.0 billion times

d)  1.0 trillion times

15.

Which of the following palindromic base sequence in DNA can be easily cut at about the middle by some particular restriction enzyme.

Explanation:

1)  Ans : b

The cutting of DNA by restriction endonucleases results in the fragments of DNA. These fragments can be separated by a technique known as gel electrophoresis. Since DNA fragments are negatively charged molecules, they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. The DNA fragments separate(resolve) according to their size through sieving effect provided by the agarose gel. Hence the smaller the fragment size, the father it moves.

2)  Ans: a

Plasmids are extrachromosomal genetic element found in any bacteria and in a eukaryotic cells. Plasmids are closed circles of double standard DNA that can exist and replicate independently of the chromosome.

3)  Ans :d

Recombinant DNA is the product obtained after isolating specific DNA and then inserting is it into another DNA molecule at a desired position. Restriction endonuclease are the enzymes that digested DNA at specific sites to isolate a specific DNA segment. Thus they are required for producing recombinant DNA.

4)  Ans :c

5)  Ans :c

Palindromic nucleotide sequences in the DNA molecule are groups of bases form the same sequence when read in both forward and backward direction.