Page 68 - CB1.3 Genetic Varation sciPAD

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68 CB 1.3 GENETIC VARIATION
USING KNOWLEDGE OF GENETICS
A sample containing DNA is
taken from a crime scene.
A sample is also obtained
from the suspects.
The DNA is isolated and added to a
vial containing restriction enzymes.
These enzymes cut the DNA into
pieces of different lengths.
The pieces of DNA are added
to an electrophoresis gel.
The smaller pieces move
further through the gel
than the larger pieces.
1
2 3
4
+ve electrode
(to power supply)
Gel supported on a
glass plate
DNA separates into different size
fragments as it travels through the gel.
5 DNA fragments in the gel are made visible by adding dyes. The fragments
appears as bands in different positions. The bands of DNA can then be
compared to the sample from the crime scene. If any of the patterns from
a suspect match the crime scene, they are highly likely to be the culprit.
-ve electrode
(to power supply)
Wells where
DNA is loaded
1. Analyse the results and identify which suspect committed the crime. 
2. Define the term ‘genetic marker’. 

DNA Profiling
DNA profiling is a technique in which individuals can be identified and compared
to others via their genetic markers. A genetic marker is a gene or DNA sequence
with a known location on a chromosome. DNA profiling is sometimes called ‘DNA
fingerprinting‘ and is commonly used in forensic science to investigate crimes.
Electrophoresis is a process where DNA fragments are added to a gel and an
electrical current is applied. DNA has a negative charge, so it moves towards a
positive terminal when electricity is applied. The fragments will move through
the gel, with the smaller fragments travelling farther in the gel than larger
fragments
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