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Bell work Objectives:

• How can understanding the DNA replication process help forensic scientists?

• I will:

▫ Explain the 3 basic steps

involved in Forensic DNA

analysis

3.3.14

DNA profiling

1. How did the DNA profiling help Kirk? 2. Why is DNA considered to have

“revolutionized” Forensic Science? 3. Why do DNA analysts keep their DNA

profile on record? 4. What does PCR (polymerase chain

reaction) do? 5. What are the different sections of our

DNA called? 6. What is a “cold-hit”?

• Video

Forensic DNA Analysis Basic Steps in Analysis

1. Extraction:

• Separates DNA from sample

3. Separation:

• Separates amplified fragments according to size.

2. Amplification or PCR (polymerase chain reaction):

• Amplifies small portions of DNA (STR regions)

1.DNA Extraction

• How did we extract DNA from the strawberries, bananas and our own cheek cells?

• http://learn.genetics.utah.edu/content/labs/extraction/

2. Amplification or PCR

• Copies sections of DNA that we are interested in

PCR Animation

• http://www.youtube.com/watch?v=2KoLnIwoZKU

▫ What steps are involved one cycle of PCR?

▫ How many copies of DNA can be made in just 30 cycles?

• http://www.dnalc.org/resources/animations/pcr.html

• http://www.nfstc.org/pdi/Subject05/images/pdi_s05_m02_01.swf

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The Thermal Cycler

Amplifies DNA

What’s going on inside the thermal cycler?

• DNA is being amplified… in cycles

• Each cycle has three steps:

1. The two DNA strands are denatured by heat.

2. The sample is then cooled to allow the primers to anneal to the DNA segments.

3. The temperature is raised to allow the DNA polymerase to add nucleotides to extend the

primers to produce a copy of each DNA template strand.

3.Separation

• Separates amplified fragments according to size.

• Ways to separate DNA:

1. Gel Electrophoresis

2. Capillary Electrophoresis

Closing Question

• What are the 3 steps of Forensic DNA Analysis?