Make your own free website on Tripod.com








FORENSIC BIOLOGY 101
Short Tandem Repeats (STR)













Home

Autopsies | Blood Analysis | Absorption-elution technique | Kastle-Meyer Colour Test | Luminol Test | Human or Not? Precipitin Test | Blood stain patterns | DNA Fingerprinting | Restriction Fragment Length Polymorphisms (RFLP's) | Short Tandem Repeats (STR) | Entamology | Common Insects | Links





donotpolice.jpg

D.N.A. Fingerprinting
















The problem with RFLP analysis is that it requires a relatively large amount of DNA, which in turn requires a relatively large
 
amount of sample. This hinders its usefulness in the field of forensics. By contrast, the Polymerase Chain Reaction allows us to
 
develop a DNA profile from as little DNA as might be deposited by licking an envelope! PCR can do this because instead of
 
cutting out the target STR sequences from the rest of the genome, it amplifies the sequences by replicating them over and over.
 
DNA is replicated by the naturally occurring enzyme DNA polymerase. In nature, the two strands of the DNA molecule are
 
replicated individually and in their entirety -- there is never replication of just one section of DNA. To force the replication of
 
specific sequences of the genome, scientists have developed special DNA primers that recognize and stick to
 
specific sequences, and enable DNA polymerase to replicate only those sequences enclosed by the primers.
 
Since we know the desired STR sequences, and we know some of the bases before and after the STR, we can
 
construct primers that will attach themselves on either side and allow replication of the sequence in-between.
















donotpolice.jpg