BME - DNA fingerprinting

DNA fingerprinting

determination of an individual’s unique collection of DNA pattern.

Used in healthcare system - diagnosis of hereditary disease, chromosome aberrations, and cancer.

Used in judicial system - identification of suspects and establishing paternity

How to do DNA fingerprinting

1. Collect tissue sample (>20 cells)

2. PCR analysis with STR RFLP

STR - Single tandem repeats

Certain regions of genome are highly variable and made of repeating base pairs

RFLP - Restriction Fragment Length Polymorphism

a technique that cuts DNA into fragments using restriction enzyme digestion to cut DNA.

Difference in DNA fragment size results from presence of different DNA sequences

Restriction enzymes (endonucleases)

Enzymes that cut DNA

Recognize specific base sequences in DNA and cut DNA only at those recognition sites

Restriction enzyme recognition site

enzymes recognize specific 4-8 bp (base pair) sequences

e.g. EcoRI recognizes GAATTC (and its pair)

e.g. PvuII recognizes CAGCTG (and its pair)

Restriction enzyme - staggered fashion

e.g. EcoRI (GAATTC)

cuts DNA at both strands, leaving overhangs. (looks like sign when cut)

Restriction enzyme - direct fashion

e.g. PvuII (CAGCTG)

cuts DNA in a straight line

Allele

one of 2+ alternative forms of a gene that can arise by mutation and are found at the same place on a chromosome

wild type allele - “normal” allele

mutant allele

different alleles act as different restriction sites, even if they differ by one nucleotide