This representation of an agarose gel shows how restriction enzyme digestion can be used to distinguish between an individual who is homozygous for a wildtype version of a gene versus individuals heterozygous or homozygous for a point mutation in that gene that creates a new restriction enzyme site. The normal region of DNA is 200 base pairs long and lacks the restriction enzyme site, so it is not cut by the enzyme. The DNA with the point mutation has the restriction enzyme site, so it is cut into 2 pieces of 180 and 20 base pairs. The DNA in each lane has been amplified by PCR prior to restriction enzyme digestion.
- Lane 1: DNA size ladder used to determine the size of the DNA fragments.
- Lane 2: DNA from an individual with the wildtype version of the gene; only the 200 base pair DNA is seen.
- Lane 3: DNA from an individual who is heterozygous for the point mutation; the normal 200 base pair DNA and the 180 and 20 base pair pieces are seen.
- Lane 4: DNA from an individual who is homozygous for the point mutation; only the 180 and 20 base pair pieces are seen.
