Eco RI and Rsa I restriction endonucleases require 6 and 4 bp sequences, respectively for cleavage. In a 10 kb DNA fragment how many probable cleavage sites are present for these enzymes?

Question

Eco RI and Rsa I restriction endonucleases require 6 and 4 bp sequences, respectively for cleavage. In a 10 kb DNA fragment how many probable cleavage sites are present for these enzymes? (A) 0 Eco RI and 10 Rsa I (B) 1 Eco RI and 29 Rsa I (C) 4 Eco RI and 69 Rsa I (D) 2 Eco RI and 39 Rsa I

Tardigrade Admin · Accepted Answer

The frequency by which a restriction enzyme will cut DNA is mainly a function of the length of the sequence, it is sensitive to, like Rsa I recognition sequence has

4

base pairs. Out of sheer probability, we see that with

4

positions and each position having potentially

4

different values there are

4^{4} = 256

different possibilities for given

4 -

base long strand. Therefore, theoretically, this enzyme will cut

1

in

2564

-base pair long sites. On the other hand, Eco RI recognises a sequence of

6

base pairs

4^{6} = 4096

possible combinations with this length. Total DNA length =

10 kb = 10, 000, b p

So, probable cleavage would be
Eco RI

= \frac{10000}{4096} = 2.44

Rsa I

= \frac{10000}{256} = 39.06

Q. Eco RI and Rsa I restriction endonucleases require 6 and 4 bp sequences, respectively for cleavage. In a 10 kb DNA fragment how many probable cleavage sites are present for these enzymes?

0 Eco RI and 10 Rsa I

1 Eco RI and 29 Rsa I

4 Eco RI and 69 Rsa I

2 Eco RI and 39 Rsa I

Q. Eco $R I$ and Rsa $I$ restriction endonucleases require $6$ and $4$ bp sequences, respectively for cleavage. In a $10$ kb DNA fragment how many probable cleavage sites are present for these enzymes?