PCR has numerous applications : 1) Gene isolation 2) Mapping of complex traits 3) Molecular taxonomy 4) Forensic science ( DNA fingerprinting) 5) Isolating ancient DNA sequences 6) Diagnosis of inherited disease.
Professor Sir Alec Jefferys of Leicester University realised in 1983 that VNTR variation due to the presence of different numbers of microsatellite repeat sequences at the same chromosomal location could be used to distinguish between individuals in a population………
DNA fingerprinting: DNA fingerprinting is based on the fact that large portions of the eucaryotic genome consists of repetitive, non-coding sequences. These repeat sequences are found all over the genome, on each chromosome and consists of repeats of the same sequence. V ariable N umber T andem R epeats VNTR’s
VNTR’s are based on the existence of microsatellite repeat sequences These are repeats of small sequences e.g. CACA These repeats are scattered throughout the genome: CACA CACA CACA CACA CACA CACA - Person A CACA CACA CACA CACA – Person B
DNA fingerprinting is based on the fact that individuals in a population have different numbers of repetitive sequences at the SAME locus.
The principle of DNA fingerprinting is VERY SIMPLE: Use PCR primers which amplify across the variable region: In different individuals, bands of different sizes will be amplified from the genome This leads to the fingerprint – unique for every individual.
Paternity profiling: Which child is least likely to be the biological offspring of this couple?
Rape Investigation: 1. Known blood sample of victim 2. Known blood sample from defendant 3. DNA size markers 4. Female fraction from vaginal swab of victim 5. Male fraction from vaginal swab of victim. Q – is the suspect (2) guilty?