Mutation and Control of Gene Expression: Sickle Cell Anaemia

Overview

Recall questions on Sickle Cell Anaemia.

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

   Define the term gene mutation.

   Model answer

   A gene mutation is a change in the base sequence of the DNA of a gene.

2. 2

   Name three types of gene mutation.

   Model answer

   Substitution, deletion and insertion.

3. 3

   Why does a deletion usually have a more serious effect than a substitution?

   Model answer

   A deletion shifts the reading frame, so every codon after it is altered and the whole polypeptide is changed.

4. 4

   Explain why some substitution mutations have no effect on the polypeptide produced.

   Model answer

   The genetic code is degenerate, so the new codon may still code for the same amino acid.

5. 5

   Which polypeptide of haemoglobin is altered in sickle cell anaemia?

   Model answer

   The β-globin chain.

6. 6

   Describe the mutation responsible for sickle cell anaemia.

   Model answer

   A single base substitution changes one codon so that valine replaces glutamic acid at the sixth position of the β-globin chain.

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