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.