Question

(a) Write the palindromic nucleotide sequence for the following DNA segment:

5′ - GAATTC - 3′

(b) Name the restriction endonuclease that recognizes this sequence. 

(c) How are ‘sticky ends’ produced? Mention their role

Answer 1

(a) 5' – GAATTC – 3' 

3' – CTTAAG – 5' 

(b) EcoRI is the restriction endonuclease that recognizes this palindrome. 

(c) When the restriction enzyme cuts the DNA strands a little away from the center of the palindromic sequence, between the same two bases on both the strands, sticky ends are produced.

• The stickiness of the ends facilitates the action of the enzyme DNA-ligase.