What does the formation of recombinant DNA result from?

Answer 1

Recombinant DNA

To to make recombinant DNA or plasmids, the two different samples of DNA need to be cut up by the same restriction enzyme. Restriction enzymes cut DNA at specific sequences (restriction sites) and is usually a staggered cut. For example, say you had the following sequence of DNA (both strands): 5' GAATTC 3'

3' CTTAAG 5'

Say the restriction enzyme used will cut a strand between a guanine and adenine on one strand and an adenine and guanine one the other strand. For the given DNA, there would be cuts where the bars are:

5' G|AATTC 3'

3' CTTAA|G 5'

Then the strands would separate:

5' G--------AATTC 3'

3' CTTAA--------G 5'

Because the cuts are staggered, hydrogen bonds are left open. The ends of the restriction fragments are called "sticky ends" because of their ability to bond to other fragments. Remember that both sets of DNA are cut with the same restriction enzyme. Therefore, the sticky ends of the restriction fragments are complementary to each other. Then you're able to take one fragment of one DNA sample and insert it into the other DNA sample, which are bound together by hydrogen bonds. DNA ligase is then added to seal the ends together.