Explain how mutations and sexual reproduction contribute to genetic variation within a population.

Cambridge International IGCSE Biology (0610) — 18.1 Variation · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Mutation causes a random change in the DNA base sequence, creating new alleles.
These new alleles increase genetic variation between individuals.
During meiosis, gametes are produced, each carrying a different combination of alleles.
Fertilisation fuses two different gametes, producing offspring with a unique combination of alleles (a new genotype).

Examiner tips

Use the word ‘mutation’ and ‘alleles’ early. Show the sequence: mutation → new allele → variation. Mention meiosis and fertilisation as the two key stages. Keep each point short and to the point.

Common mistakes

Confusing mutation with natural selection. Using vague terms like ‘different’ without specifying alleles. Omitting the role of fertilisation in creating new combinations.

Mark scheme (4 marks)

Mutation causes a random change in the base sequence of DNA
New alleles formed by mutation increase genetic variation between individuals
During meiosis, gametes are produced each with a different combination of alleles
Fusion of two different gametes at fertilisation produces offspring with a new, unique combination of alleles / genotype

Key terms in this question

mutation · genetic variation