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Published bySusan Matthews Modified over 6 years ago
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Aim: How do scientists identify people using DNA Fingerprinting?
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Why do we Fingerprint? So we can identify people
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Why is DNA used to identify people?
People have different DNA base sequences, therefore each individual will have a different DNA fingerprint.
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ATTGCCTAGG - Individual 1 ATTGCCATGG - Individual 2
Genetic Markers: ATTGCCTAGG - Individual 1 ATTGCCATGG - Individual 2 Are particular segment of DNA on a chromosome. Can use to trace heredity Our noncoding regions are highly variable from one individual to another and serve as good genetic markers to be used for DNA fingerprinting.
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How do scientists make a DNA Fingerprint?
Investigators need to find some DNA of the perpetrator. Where can investigators find the DNA? Blood 2) Hair 3) Nails 4) Skin
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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).
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PCR Animation http://learn.genetics.utah.edu/content/labs/pcr/
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Gel Electrophoresis Amplified DNA is cut 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.
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Gel Electrophoresis DNA is negatively charged & moves through the gel to the positive side. 5) Smaller segments move faster & farther than the larger segments.
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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.
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Gel Electrophoresis virtual demo
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- + Gel Electrophoresis DNA Suspect A Suspect B Suspect C from CS
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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?
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