DNA Profiling

Seite 1

DNA Profiling

The human genome

It is all the genetic material an organism contains.

DNA is found in the nucleus and the mitochondria.

Genes that code for proteins only make up about 2% of all DNA in cells. These are called exons.

Non-coding regions of DNA are removed from mRNA before its translated. These are called introns.

Satellite DNA

Short sequences of repeated DNA in introns.

Minisatellites – also called VNTRs (variable number tandem repeats)

20-50 base pairs longs.

In every intron they are repeated 50-several 100 times.

More than 1000 locations.

Microsatellites

2-4 bases long.

Repeated 5-15 times.

STRs – short tandem repeats. Another name for microsatellite.

DNA profiles

Satellites appear in the same place on the chromosomes.

Number of repeats vary between individuals.

Different lengths of inherited from both parents.

Only identical twins have the same patterns.

Close relative patterns are similar.

An image of these patterns is known as a DNA profile.

SIR ALEC JEFFREY’S WORK

How’s a DNA profile done?

DNA cut with restriction enzymes.

Fragments separated by gel electrophoresis.

Cut at defined points in introns so leave some repeats and satellite regions intact.

Fragments stained to reveal a binding pattern.

Applications

Forensics

Identifying Nazi war criminals

Identifying remains

Match profiles from descendants of soldiers of war.

Paternity

Half of STRs from Mum and half from Dad.

Comparing DNA profiles will establish paternity.

Half child’s genetic information from Mum and half from Dad.

Disease detection

Protein electrophoresis detects type of haemoglobin present in a blood sample.

This can aid diagnosis of sickle cell anaemia.

Or varying number of repeat sequences for a condition such as Huntington’s disease.