VNTR D1S80

Hi!

Gel electrophoresis works by separating molecules based upon charge, size and shape. In the case of VNTR D1S80, the repeat unit is 16 base pairs long. This means that the sequence of nucleotides repeated in tandem within this VNTR locus consists of 16 base pairs. The variations in the number of repeat units, which may range from a few to several dozen, result in different-sized alleles on gel electrophoresis. On the other hand, VNTR D17S30 has a repeat unit of 70 base pairs. The DNA sequence within this VNTR locus contains a different set of nucleotides repeated in tandem, with each repeat unit consisting of 70 base pairs.

What do you mean by "But why is that."?

According to the following article:

D1S80 is a VNTR region located on human chromosome 1 and consists of a 16-base pair-long repeat unit. Most people have between 14 and 41 copies of this repeat, resulting in D1S80 alleles with repeat regions of 224 to 656 base pairs in length.