PCR A license to do molecular biology

DNA FINGERPRINTING BY PCR

POLYMORPHIC DNA

• Chromosomal regions that vary widely from individual to individual

• By examining several of these polymorphic regions within the DNA, one may obtain a “DNA fingerprint”

•Can identify criminals

•Can determine paternity

•Can identify human remains

•Serve as markers for certain diseases

•Most commonly used polymorphisms are those which vary in length

•FLPS-fragment length polymorphism

•When amplified by PCR referred to as AmpliFLPs

VNTR

• Variable number of tandem repeats

• FLPs that contain specific sequences duplicated a variable # of times

D1S80

• Is a specific type of VNTR

• Located on chromosome 1

• Contains a 16 nucleotide sequence

• Variable repeated 16-40 times

• D1S80 locus is one VNTR used by FBI

• An individual who is homozygous For the D1S80 genotype will have equal

repeat numbers on both homologues of chromosome 1

• Yields a single PCR product seen on gel

• An individual who is heterozygous for the D1S80 genotype will have different D1S80 repeat numbers

• Yields 2 distinct PCR products seen on gel

http://www.biology.washington.edu/fingerprint/vntr02.gif