Class 12th Biology 2017 Set3 Outside Delhi Board Paper Solution
(a) Explain the significance of "palindromic nucleotide sequenceâ in the formation of recombinant DNA.
(b) Write the use of restriction endonuclease in the above process.
(a) The palindromic nucleotide sequence serves as recognition sites of DNA by which it binds to the site and cuts each of the two strands of the double helix at specific points by hydrolysing the phosphodiester backbones.
The palindromic DNA is a sequences of base pairs that reads same on both the DNA strands, when orientation of reading is kept the same.
eg :
5' —— GAATTC —— 3'
3' —— CTTAAG —— 5'
(b) Use of restriction endonuclease in the above process:
Restriction enzymes cut the strands of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands.
This leaves single stranded portions at the end.
There are overhanging stretchs called sticky ends on each strand. The stickyness of the ends facilitates the action of the enzymes DNA ligase.
Restriction endonuclease are used in genetic engineering to form recombination molecule of DNA, which are composed of DNA from different source/genomes.
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