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Modern Genetics

Using gene sequencing

  • 3 things to know
  • Papers 1 and 3

Overview

Recall questions on genomes, the denaturation, annealing and extension steps of PCR, how gene sequencing predicts protein structure and identifies mutations, and DNA profiling for forensics and paternity, with when to use each technique.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Numbers

Describe the extension step of PCR, and explain why the temperature is raised to 72°C.

Key term

What is a genome?

Key term

What is PCR and what is its purpose?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is a genome?

    Model answer

    The entire genetic material of an organism, comprising all of its DNA including all genes and non-coding sequences.

  2. 2

    What is PCR and what is its purpose?

    Model answer

    PCR (polymerase chain reaction) is a technique used to amplify small samples of DNA to produce many copies.

  3. 3

    What happens during the denaturation step of PCR?

    Model answer

    Heating to approximately 95°C separates the double-stranded DNA into two single strands.

  4. 4

    What occurs during the annealing step of PCR and at what temperature?

    Model answer

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

  5. 5

    Describe the extension step of PCR.

    Model answer

    Heating to approximately 72°C allows DNA polymerase to synthesise new complementary DNA strands using the primers as starting points.

  6. 6

    Why is the temperature raised to 72°C during the extension phase of PCR?

    Model answer

    This is the optimum temperature for DNA polymerase (typically Taq polymerase) to synthesise new DNA strands.

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