DNA Fingerprinting using VNTR's

On some human chromosomes, a short sequence of DNA has been repeated a number of times. In any particular chromosomes the repeat number may vary from one to thirty repeats. Since these repeat regions are usually bounded by specific restriction enzyme sites, it is possible to cut out the segment of the chromosome containing this variable number of tandem repeats or VNTR's, run the total DNA on a gel, and identify the VNTR's by hybridization with a probe specific for the DNA sequence of the repeat.

Shown to the right at the top are the chromosomes of the two parental individuals of the pedigree below. The first individual has one chromosome with 4 repeated sequences and one chromosome with 6 repeated sequences. The other individual has one chromosome with 3 repeated sequences and one chromosome with 5 repeated sequences.

At the bottom of the figure is a pedigree of the mating between these two individuals and their four children. The DNA of each of the individuals has been analyzed for the VNTR repeat number and the gels are show below each individual along with the genotype for each individual. Notice that each of the six people are distinguishable from each other by the VNTR's at this one genetic locus. If several VNTR loci were used, the uniqueness of each individual would become even more distinct.

 

From: BIOL 121 Human Biology Web Site. The Human Biology course was developed by Robert J. Huskey and Fred A. Diehl.