Question

The restriction endonuelease EcoR-1 recognises and cleaves DNA sequence as shown below
5' - G A A T T C - 3'
3' - C T T A A G - 5'
What is the probable number of cleavage sites that can occur in a 10 kb long random DNA sequence ?

• A. 10
• B. 2
• C. 100
• D. 50

Answer 1

Answer: (B)

2

The restriction enzyme EcoRI is a 6 base cutter and the DNA sequence is composed of 4 nucleotide bases. So, the probable number of cleavage is 1/4${}^6$= 0.00024. The length of the DNA sequence is given as 10 kb (10000 bp). So, the probable number of cleavage sites in the 10 kb segment are 10000 x 0.00024= 2.4

Thus the correct answer is option B.