DNA fingerprinting

Question 1

What is DNA fingerprinting?

Answer 1

A technique that simultaneously detects lots of minisatellites in the genome to produce a pattern unique to that individual

Question 2

How was the first DNA fingerprint produced?

Answer 2

• Extract DNA (same as in profiling)
• restriction enzymes cut the DNA, resulting in thousands of pieces of DNA at a variety of lengths
• Gel electrophoresis then separated the DNA accroding to size
• Then the DNA was ‘blotted’ onto a nylon membrane and ‘unzipped’ to produced ssDNA
• The nylon membrane was incubated with radioactive probes which are small fragments of minisattelite DNA tagged with radioactive phosphorous and they only attach to complemenrary DNA
• The minisatellite that the probes have attached to were then visualised by exposing the nylong membrane to X-ray film producing a DNA fingerprint

Question 3

Compare DNA fingerprinting to DNA profiling

Answer 3

• DNA profiling relies on Microsatellites (STRs) as opposed to the minisatellites as used in DNA fingerprinting
• Both minisatellites and microsatellites are repeated throughout the genome

DNA profiling
* DNA extracted, STR analysis is senstivie so only need a small amount
* DNA profiling uses PCR instead of restriction enzymes to produce many copies of the specific sequence
* uses flourescent tags as opposed to radioactive labelling
* both use electrophoresis to separate fragments according to size
* in profiling the fragments passes by a laser which causes the tags to glow with a specific colour which highlights the colour and length of each STR