DNA profiling

What is a DNA profile?

a fingerprint of an organisms DNA (unique to the individual unless you are identical twins)

• used to identify people

• to determine genetic relationships

How is a DNA profile made?

1. DNA sample is taken from blood or saliva etc

2. PCR is used to amplify the DNA

3. A fluorescent tag added so that the DNA can be viewed under a UV (in a lab) (in a class room you stain after fragments are separated)

4. Gel electrophoresis is used to separate the DNA

5. Gel is observed under a UV light

6. Two DNA profiles can be compared to find the similarities to identify the person

Method of a PCR

1. A mixture containing the DNA sample, free nucleotides, primers and DNA polymerase

2. DNA mixture is heated to 95 degrees to break hydrogen bonds splits the DNA

3. The mixture cooled to 50-65 degrees

4. This binds (anneals) the primers to the strands

5. The reaction mixture heated to 72 degrees so DNA polymerase works

6. DNA polymerase lines the free nucleotides along the template strand

7. Complementary base pairing creates new complementary strands

8. Two new copies of the fragment of DNA are formed in the first cycle

9. The cycle is repeated and doubles the number of fragments

Method of Gel electrophoresis

1. Buffer solution is added to the slab of agarose gel

2. DNA is placed using a micropipette into a well in the agarose gel next to the cathode and covered in a buffer solution making sure not to pierce the bottom of the gel

3. Repeat and add the other DNA using fresh tips each time

4. The buffer solution conducts electricity

5. An electrical current is passed through the gel

6. DNA is negatively charged and they become attracted to the anode

7. Short DNA fragments will move faster and travel further as they are lighter

8. DNA fragments are separated by length

What can DNA profiling be used for?

In a forensic scene to identify people

• DNA is collected from the crime scene

• DNA is isolated and amplified with a PCR

• They can use gel electrophoresis and the DNA profiles

• DNA profiles compared to suspects

Determining genetic relationships in humans

• comparing DNA of child and potential parent

• the more bands in common, the more related

• one parent will make up half of the DNA

To prevent inbreeding in plants and animals

• to decrease the risk of genetic disorders that lead to health disorders

• Inbreeding decreases the gene pool

• DNA profiling finds out how closely related the individuals are

• the least related individuals will be bred together