How do scientists identify people using DNA Fingerprinting?

1) Why do we Fingerprint? So we can identify people

2) Why is DNA used to identify people? People have different DNA base sequences, therefore each individual will have a different DNA fingerprint.

3) Genetic Markers: ATTGCCTAGG - Individual 1 ATTGCCATGG - Individual 2 Are particular stretches of DNA that are variable among individuals. Our noncoding regions are highly variable from one individual to another and serve as good genetic markers to be used for DNA fingerprinting.

4) How do scientists make a DNA Fingerprint? Investigators need to find some DNA of the perpetrator. a) Where can the investigators find the DNA? Blood Hair Nails Skin

b) What if you only find very little DNA? Polymerase Chain Reaction: PCR The sample of DNA is then amplified (multiplied) using a process called Polymerase Chain Reaction (PCR).

PCR Animation

5) Gel Electrophoresis Amplified DNA is treated with specific restriction enzymes. 2) DNA segments are loaded into wells in a porous gel. 3) Electric current is passed through the gel making one side of the gel + charged and one side – charged.

5) Gel Electrophoresis DNA is negatively charged & moves through the gel to the positive side. 5) Smaller segments move faster & farther than the larger segments.

5) Gel Electrophoresis 6) The gel is then stained so we can see the DNA banding patterns. Result: The smaller segments of DNA are found closer to the positive end than the larger segments. **Separates DNA segments according to SIZE.

- + Gel Electrophoresis __ __ __ __ __ __ __ __ __ __ DNA Suspect A Suspect B Suspect C from CS __ __ __ __ __ __ __ __ __ __ +

DNA Fingerprint Questions: What is the charge of DNA? Where would we find the smallest DNA fragments, closer to the + end or the – end? Why do we get different banding patterns for each individual? 4) Which suspect was at the crime scene?