DNA profiling, PCR and gel electrophoresis

Overview

What a DNA profile relies on and its forensic and medical uses, the three temperature steps of PCR and why Taq polymerase is used, and how electrophoresis separates fragments.

What you need to know

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Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is DNA profiling and what does it rely on?

   Model answer

   DNA profiling produces a unique pattern of DNA fragments that can identify individuals, based on variations in non-coding repetitive sequences.

2. 2

   How is DNA profiling applied in forensic science?

   Model answer

   It is used to match biological samples from crime scenes to suspects or victims.

3. 3

   How can DNA profiling be used in medicine?

   Model answer

   It is used in analysis of disease risk by identifying genetic markers associated with inherited conditions.

4. 4

   What is the polymerase chain reaction (PCR)?

   Model answer

   A technique that amplifies specific DNA sequences to produce millions of copies from a small sample.

5. 5

   What happens during the denaturation step of PCR and at what temperature does it occur?

   Model answer

   At approximately 95°C, the double-stranded DNA separates into two single strands.

6. 6

   Describe the annealing step of PCR, including the temperature used.

   Model answer

   At approximately 55°C, primers bind to complementary sequences on the single-stranded DNA.

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