1. Title of Notes
p. 9 RS
DNA Fingerprinting

2. I can describe how DNA fingerprinting is done.
Learning target
I can describe how DNA fingerprinting is done.
Today I am…
Actively engaged in reading about DNA fingerprinting.
So that I’ll be able to…
understand how important DNA fingerprinting is to crime investigation.
I’ll know I’ve got it when…
Complete all notes and homework.

3. Genetic fingerprinting
90% or more of DNA does not carry nucleotide triplets that code
for proteins
The non-coding DNA is often called ‘junk DNA’ but this only
means that its functions have not yet been discovered
Some of the non-coding regions consist of repeated sequences
of nucleotides
For example -C-A-T-G-C-A-T-G-C-A-T-G-C-A-T-G- *
* The number of repeated sequences may be much greater than this; perhaps consisting of a thousand or more base pairs
The number of repeats in any one section of DNA varies
from one individual to the next
Since these sections do not code for proteins (and, therefore are
not genes) there is no observable difference in these individuals

4. Why Use DNA Fingerprinting?
DNA fingerprinting is a way of telling individuals of the same species apart
DNA sequences are variable and can therefore be used as identifying characteristics.
DNA fingerprinting has advantages over other sources of evidence (fingerprints, blood type, etc.):
Highly accurate.
Can be gathered from trace crime scene evidence.

5. How do you take a DNA fingerprint?
Restriction enzymes are molecules that can cut DNA into pieces --> each enzyme cuts at a very specific DNA sequence
While all human beings share roughly the same DNA sequence, there are in fact a small number of differences  these differences can be seen by restriction enzymes

6. Restriction enzymes restriction enzyme cuts here…….………and…...….………here
Particular repeat sequences can be ‘cut out’ by restriction enzymes
For example
restriction enzyme cuts
here…….………and…...….………here
-CCACGACATGCATGCATGCATGCATGCATGCCACAT-
The cutting sites are the same but one restriction fragment is longer than the other

7. Gel electrophoresis
The different sized fragments are separated by a process
called gel electrophoresis
The separation takes place in a sheet of a firm but
jelly-like substance (a ‘gel’)
Samples of the DNA extracts are placed in shallow
cavities (‘wells’) cut into one end of the gel
A voltage is applied to opposite ends of the gel
Separation of the fragments may take an hour or more depending on the voltage applied
DNA has a negative charge and moves slowly towards
the positive end
The shorter fragments travel through the gel faster than the
longer fragments

8. Gel electrophoresis DNA extract added well gelatinous sheet solution
The solution is a ‘buffer solution’ which stops the gel from drying out but does not affect the separation process
solution

9. Gel Electrophoresis
Different banding patterns from different individuals

10. Appearance of separated fragments on gel
starting positions

11. DNA fingerprinting facts
Essentially, once the DNA has been cut by the enzymes, we will have DNA fragments of various sizes
Each individual’s banding patterns should be different because the restriction enzymes will cut each person’s DNA at different points
Fragments of different sizes will travel different distances along a gel when an electric current is passed through it

12. DNA fingerprinting Pages 262 -264
Reading
DNA fingerprinting
Pages
Write down two facts from the reading that are not already in your notes. Bullet point the facts.

13. Gel Electrophoresis Video
8 minutes
We will watch this video in class