12: DNA fingerprinting Flashcards
What are the steps of DNA fingerprinting?
The steps of DNA fingerprinting are
1) Extract DNA from both forensic evidence and suspect
2) Perform PCR (polymerase chain reaction) of 8+ microsatelleite loci)
3) Perform gel eletrophoresis of PCR product to obtain genotype
4) Determine probability of obtaining a match. `
What are the three steps of a polymerase chain reaction?
The three steps of a polymerase chain reaction are
1) Denaturation (separates strands)
2) Annealing (primers bind to target)
3) Extension (Taq polymerase extends DNA bonded to primer)
What is gel electrophoresis?
Gel eletrophoresis serves to call (name) alleles by size of PCR fragment by no. of bps by fractionating, visualising, and estimating size of nucleic acids.
How does gel eletrophoresis work??
DNA is -vely charged, so when an electric field is applied to a sample of DNA fragments, the DNA moved towards the +ve electrode. In gel electrophoresis this takes place in a porous gel medium that allows smaller DNA molecules to move faster towards this pole while larger fragments are hindered, resulting in sample fractionating into a spectrum of fragments by size.
What sort of markers does DNA fingerprinting rely on?
DNA fingerprinting relies on markers that..
+ Have fast rates of evolution (so are highly polymorphic)
+ Are co-dominant
A DNA marker is the best sort of marker for DNA fingerprinting because has simple inheritence (no epistasis as with morphological traits) and are abundant. More specifically, the DNA marker type forming the basis of DNA fingerprinting is a microsatelleite marker.
What is a marker?
A marker is a quantifiable character that marks underlying genetic differences between individuals
- Can be morphological or molecular
- Can be chemical, proteins, or DNA
What are microsatelleites?
Microsatelleites are regions of a (eukaryotic) chromosome containing multiple copies of short tandem repeats (STRs).
