Question

Listed below are two different single strands of DNA. Which of these, in their double-stranded form would you expect to be cleaved by a restriction enzyme? a) CTCGCCAATTGACTCGTC b) ACTCCACTCCCGACTCCA For each answer explain why or why not, using the bases of the specific example.

Answer 1

First let us draw the double strands for each given single strands of DNA

a) 5' - CTC GCC AAT TGA CTC GTC - 3'

3' - GAG CGG TTA ACT GAG CAG - 5'

b) 5' - ACT CCA CTC CCG ACT CCA - 3'

3' - TGA GGT GAG GGC TGA GGT - 5'

Now check for palindromic sequences in both the strands. In the strand (a) the palindromic sequence is present and is in bold. A palindromic sequence is a sequence that is read same in both the strands and hence the restriction enzyme will cleave strand (a).

In strand (b) there is no palindromic sequence and hence no restriction site will be present thereby it wont be cut by any restriction enzyme.

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