dna fingerprinting

1. DNA Fingerprinting
By Logan Briggs

2. Step 1
• Obtain DNA sample for use
• If sample is too small, replicate using PCR
(polymerase chain reaction)
• This is a process that uses the heating and
cooling of DNA with added primers,
polymerase, and nitrogen bases to
exponentially replicate DNA

3. Step 2
• Add restriction enzymes to cut DNA into
specific genes and loading dye to weigh down
and make the DNA visible

4. Step 3
• Add DNA to gel at negative end in wells
• Run an electric current through the gel
• DNA will separate out into bands in the gel
• This is called gel electrophoresis

5. Why does this happen?
• The DNA is negatively charged, so when it is
placed in the gel and an electric current is run
through it, it will migrate from the negative
end where it is placed to the positive end.
The bands are formed from the different
lengths of DNA, as cut by the enzymes. The
larger pieces won’t move as far through the
gel, but smaller pieces will, thus forming
bands

6. Step 5
• Move to nylon membrane
• Coat membrane with gene specific radioactive
probes
• Transfer DNA from gel to membrane
• Radioactive probes attach to certain parts of
DNA

7. Why does this happen?
• During the gel electrophoresis, the hydrogen
bonds in the DNA are broken, making it single
stranded
• The single stranded probes bond to the
complimentary DNA

8. Step 6
• Expose X-Ray film to membrane
• Band pattern from probes will show up. This is
the DNA fingerprint

9. DNA fingerprinting uses
• Identifying criminals from evidence at crime
scenes
• Determining if certain traits or diseases are
being passed down genetically
• Determining if two animals should breed
together
• Tracking paths and origins of diseases

10. Special advantages
• Not having to sequence entire DNA
• Being able to identify someone’s DNA quickly
using only a few genes, but it still being a 1 in
100 billion chance of two people having same
DNA fingerprint
• Very accurate

11. The future?
• Being able to use smaller amounts of DNA;
not having to waste as much time copying it
• Being able to do it faster
• Using it for medical matches, such as organ
donors