Whose DNA Was Left
Behind?
Edvotek Europe
What are we
doing today?
• Introduction
• Load gels
• Electrophoresis
• Analyse results
Why study DNA?
Ready to load kits
• S51 Whose DNA Left Behind?
– Dye based electrophoresis
– Quick - no staining required
– Colourful result!
Health & safety
• No toxic chemicals
• Safe solutions and reagents used in
place of research materials
Your crime to
solve
Lisa’s saxophone
has been stolen!
The Scene of the
Crime
Lisa’s room.
Blood
found on
the
saxophone
case.
Suspect 1Homer Simpson
Suspect 2Krusty the Klown
Compare samples
• Use electrophoresis
• Micropipette to load samples
• Electrical current will separate by
size
• Pattern is DNA fingerprint
Gel casting
Running buffer
TAE buffer
• 20ml 50x buffer to 1 litre with water
• Distilled water ideal but tap ok
• Can be reused a few times
• Store unused for future use ok
Agarose
0.8% Agarose
• 3g in 375 ml dilute buffer
• Melt in microwave/autoclave
• Pour when hand hot
Agarose
• Store gels for 1-2 weeks in fridge
wrapped in cling film or plastic bag
• Keep any left over gels and remelt
next time
The experiment
Prepare gel
Dry loading
• Load gel dry not through buffer!
• Do not puncture bottom of well
• Change tips between each sample
Gel Loading
Load 40 l of each sample into the wells
A
B
Crime
Scene
C
D
Suspect 1
Homer
E
F
Suspect 2
Krusty
Run gels
• Put on lid and attach to power
supply
• Run for 15-20 minutes at 150 volts
• Or 75 volts for 30-40 minutes
• Check for bubbles at electrode
What is DNA fingerprinting?
DNA fingerprint
• Get DNA from someone
• Cut it up with enzymes
• Separate different size bits on a gel
• Pattern is a DNA fingerprint
Get some DNA
DNA is very long
• 2 metres per cell!
• 3 billion letters long (ACTG)
• Like a piece of string
• Cut with scissors
Where to cut?
• Decided by combination of letters
GTTAAC is cut by one sort of enzyme
TTAA cut by a different sort
Real enzymes
Separate on gel
• Made of seaweed - agarose
• Different size pieces move through
mesh - like a sieve
• Small move quicker than big
• Called DNA electrophoresis!
move by size
big
medium
small
Analyse results
Lanes 1 & 2- Crime Scene DNA
Lanes 3 & 4
Lanes 5 & 6
Suspect 1- Homer
Suspect 2- Krusty
Result
CS
A B
1
2
3
S1
C D
S2
E F
Time to make the
arrest
Thank you
• DNA experiments can be carried
out easily
• Fun and relevant to wider world
• Promote understanding