Question

(a) Write the palindromic nucleotide sequence for following sequence of DNA segment: 
5' – GAATTC – 3' 
(b) Name the restriction endonuclease that recognizes this sequence. 
(c) How are sticky ends produced? Mention their role.

Hint:

Sticky ends produced by restriction enzymes like EcoRI help in easy and specific joining of DNA fragments in recombinant DNA technology.

Answer 1

Step 1 (a): The palindromic sequence of 5' – GAATTC – 3' is: 
5' – GAATTC – 3' 
3' – CTTAAG – 5' 
It reads the same in 5' to 3' direction on both strands, making it a palindrome. 

Step 2 (b): The restriction endonuclease that recognizes this sequence is EcoRI. 

Step 3 (c): EcoRI cuts between G and A in both strands as follows: 
5' – G↓AATTC – 3' 
3' – CTTAA↑G – 5' 
This creates **sticky ends** (overhanging single-stranded regions) which can form hydrogen bonds with complementary sequences. 

Step 4: Sticky ends facilitate the insertion of foreign DNA during genetic engineering by allowing ligation with complementary sequences.