Question

Observe the given sequence of nitrogenous bases on a DNA fragment and answer the following questions:

(a) Name the restriction enzyme which can recognise the DNA sequence. 
(b) Write the sequence after restriction enzyme cut the palindrome. 
(c) Why are the ends generated after digestion called as ‘Sticky Ends’?

Hint:

Sticky ends are useful in genetic engineering because they allow precise joining of DNA fragments with complementary overhangs, such as those created by EcoRI.

Answer 1

Step 1: For (a), the sequence 5'-GAATTC-3' (and its complement 3'-CTTAAG-5') is a palindrome recognized by the restriction enzyme EcoRI, which cuts between G and A.
Step 2: For (b), EcoRI cuts 5'-CAGAATTC TTA-3' into 5'-CAG-3' and 5'-AATTCTTA-3', and the complementary strand 3'-GTCTTAA GAA T-5' into 3'-GTC-5' and 3'-TTAAGAA T-5'. The resulting fragments are 5'-CAG-3' with 3'-GTC-5', and 5'-AATTCTTA-3' with 3'-TTAAGAA T-5'.
Step 3: For (c), the ends are called "Sticky Ends" because the cut by EcoRI leaves single-stranded overhangs (5'-AATT-3' on one fragment and 3'-TTAA-5' on the other), which can base-pair with complementary overhangs on other DNA fragments, facilitating ligation.
Thus, the enzyme is EcoRI, the fragments are as described, and the ends are sticky due to their overhanging sequences.