Question

The restriction endonuclease Not I cuts DNA at the recognition sequence GCGGCCGC. At what frequency do you expect this sequence to be found in a random sample of long DNA? Choose the best answer.

Select one:

once in 6 bases

once in 256 bases

once in 1024 bases

once in 4096 bases

once in 65,536 bases

Answer 1

Once in 65536

We consider only one strand of DNA because the same sequence will be present on opposite strand at same site due to symmetry of sequences. The enzyme cuts 8 base long sequence, and there are 4 bases(A,T,G,C) in DNA.so that 8 positions can be occupied by 4 different bases,the possibility to get the sequence cut by the enzyme is (1/4)8.this possibility is the frequency of cutting by enzyme 1 in 48 sequence can be GCGGCCGC.so frequency =(1/4)8 =1 in 65536.