Question

EcoRI recognizes the sequence 5'-G|AATTC-3' (""|"" indicates the point of cleavage). Treatment of the following oligonucleotide with EcoRI would produce two oligonucleotides with sizes of _____ double-stranded nucleotides containing _____ ends.

5'-CAAGTCGATACAGAATTCGTACCTAG-3'
a) 13; blunt
b) 15; sticky
c) 17; sticky
d) 19; blunt

Answer 1

After EcoRI treatment, the oligonucleotide would produce two fragments of 13 and 15 nucleotides each with sticky ends.

Step-by-step explanation:

The student has asked about the size of the fragments and the type of ends produced after the treatment of a given oligonucleotide with the EcoRI enzyme. EcoRI recognizes the specific sequence 5'-G|AATTC-3' and cuts at this site, producing sticky ends. In the given sequence, 5'-CAAGTCGATACAGAATTCGTACCTAG-3', EcoRI would cut after the G within the sequence GAATTC, resulting in two fragments.

Counting the nucleotides from either end to the cleavage site, we find that the left fragment would contain 12 nucleotides (5'-CAAGTCGATACA-3') and the right fragment would have 14 nucleotides (5'-GTTACGTAGG-3'). Therefore, the answer is (c) 13 and 15, respectively; with sticky ends because of the overhanging sequences at the ends of the cuts made by EcoRI which can base pair with complementary sticky ends of other DNA fragments.