What is mutation? Explain its types with examples.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define. A mutation is a sudden change in the genetic material that can be inherited. Hugo de Vries coined the term.
2 · Gene mutation. A change in the base sequence of a gene by substitution, deletion or insertion, e.g. sickle cell anaemia.
3 · Chromosomal: structure.
Deletion: a part is lost.
Duplication: a part is repeated.
Inversion: a part is turned round.
Translocation: a part moves to another chromosome.
4 · Draw the structural changes. [Diagram: a chromosome ABCDEF; deletion ABDEF; duplication ABCCDEF; inversion ADCBEF; translocation: a piece moved to another chromosome]
5 · Chromosomal: number.
Euploidy: whole sets added (polyploidy, 3n or 4n), e.g. seedless watermelon.
Aneuploidy: 2n + 1 or 2n − 1, e.g. Down syndrome (trisomy 21).
6 · Causes. Mutagens such as X-rays, UV rays and some chemicals.
7 · Link to daily life. Seedless watermelons and bananas are polyploids; avoid unnecessary X-rays.
8 · Close. Mutations are the source of new variation and the raw material of evolution.
Scoring tip: Use the letters ABCDEF to show each structural change. It is quick, clear and examiners like it.
