Photograph of illuminating DNA fragments on gel under ultraviolet light after electrophoresis.

<p>DNA bands in lane 1, 2 and 3 indicate successful amplification of the target sequence. The gel also shows a positive control, and a DNA ladder containing DNA fragments of defined length for sizing the bands in the experimental PCRs. Lane 1: homozygous patient for LL alleles, Lane 2: homozygous patient for SS alleles; Lane 3: heterozygous patient for LS alleles (L = long, S = short).