2.  Restriction Enzymes are part of the essential tools of genetic engineering. They have the ability to cut DNA molecules at very precise sequences of 4 to 8 base pairs called recognition sites. These enzymes allow genetic engineers to cut up DNA in a controlled way.  The sites where the fragments of DNA are cut may result in overhanging sticky ends or non- overhanging blunt ends. Pieces are later joined together by DNA ligase.

4.  Sticky ends are ends with exposed nucleotide bases at each end. Restriction enzymes may cut DNA leaving an overhang or sticky end. DNA cut like this is able to join to other exposed fragments of DNA with matching sticky ends. These joins are specific to their recognition sites.  1.A restriction enzyme cuts the double-stranded DNA molecule at its specific recognition site  2. The cuts produce a DNA fragment with two sticky ends. The piece its removed from is also left with sticky ends.

5.  Blunt ends are ends with no exposed nucleotide bases at each end. It is possible to use restriction enzymes that cut leaving no overhang. DNA cut like this is able to join to any blunt end fragment but is nonspecific because there are no sticky ends as recognition sites.  1. A restriction enzyme cuts the double-stranded DNA molecule at its specific recognition site.  The cuts produce a DNA fragment with two blunt ends. The piece it is removed from is left with blunt ends.

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