Genetic Fingerprinting and Recombinant DNA Technology

Overview

Recall questions on PCR.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Which parts of the genome are used to produce a genetic fingerprint?

   Model answer

   Non-coding regions containing short sequences of bases repeated many times over, known as variable number tandem repeats.

2. 2

   What does the polymerase chain reaction achieve?

   Model answer

   It makes millions of copies of a chosen length of DNA in a test tube, so that a very small sample becomes large enough to analyse.

3. 3

   Which components must be placed in the reaction tube for PCR?

   Model answer

   The DNA sample, two primers, a supply of free DNA nucleotides, thermostable DNA polymerase and a buffer solution.

4. 4

   What happens to the DNA when the mixture is heated to 95 °C?

   Model answer

   The hydrogen bonds between the complementary bases break, so the double helix separates into two single strands.

5. 5

   Why is the mixture then cooled to about 55 °C?

   Model answer

   So that the primers can anneal by base pairing to the complementary sequences at each end of the target length of DNA.

6. 6

   State two functions of the primers in PCR.

   Model answer

   They provide the starting point at which DNA polymerase can begin adding nucleotides, and they define which region of the DNA is copied.

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