Genetic fingerprinting

What is a ‘genetic fingerprint’ and when is it used

It is the unique sequence of bases in your genome

Its used in paternity and forensic cases

Explain the premise for genetic fingerprinting

It bases the idea off the fact that a gene has sections know as exons which are translated and introns which aren’t. The introns contain blocks of repeating bases called short tandem repeats. these vary between individuals and when undergone GF you can produce a unique pattern of these STRs to identify the individual

Explain the first main step in genetic fingerprinting

PCR - polymerase chain reaction - this is used to amplify the DNA so that their is more for the gentic fingerprinting

1. create the DNA sample mix containing

• free DNA nucleotides

• sample DNA

• TAQ polymerase - has a higher optimal temp without denaturing - thermo stable

• primers - to anneal the sample DNA to the free nucleotides - makes it complementary 7

2. Use a thermocycler to make variant temps

3. Starting with 95 degrees to break hydrogen bonds in DNA

4. cool to 60 degrees to allow the primers to anneal

5. heat to 72 degrees for TAQ P to join to the DNA and primers the free nucleotides to template strand

6. This produces 2 new copies of the DNA strand in one cycle and this repeats 30-40x

Explain the next step in genetic fingerprinting

Gel electrophoresis

1. The DNA strands are placed in agarose gel

2. A voltage is then put across and the negatively charged DNA move towards the positive cathode

3. The distance they travel across the gel is down to the size of the DNA - STRS as shorter ones can travel faster so travel further

4. This creates a DNA profile to compare

5. A DNA ladder is run alongside to compare fragment position and size

Explain how its used

It is then compared eg. in paternity tests against mother and father as STRs are heritable