Describe how the process of sexual reproduction leads to genetic variation in offspring.

Eduqas GCSE Biology — 2.4.1 Variation · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

Sexual reproduction involves the fusion of male and female gametes (fertilisation). Gametes are haploid, so each parent contributes only half the chromosome number and different alleles. The offspring inherit a new combination of alleles from both parents, giving a genotype that differs from either parent. These new allele combinations produce different phenotypes, creating genetic variation among offspring.

Examiner tips

Use the exact terms: fertilisation, haploid, alleles, genotype, phenotype
Show the step‑by‑step flow: gamete fusion → haploid contribution → new allele mix → varied phenotype
Keep each point short and to the point to hit all four marks

Common mistakes

Confusing fertilisation with meiosis; describing only meiosis without fertilisation
Using ‘diploid’ instead of ‘haploid’ for gametes
Failing to mention that the new allele combination is different from both parents

Mark scheme (4 marks)

Sexual reproduction involves the fusion of male and female gametes (fertilisation)
Gametes contain half the usual number of chromosomes (are haploid), so each parent contributes different alleles
Offspring inherit alleles from both parents, giving a different combination of alleles (genotype) to either parent
Different combinations of alleles result in different phenotypes / characteristics among offspring

Key terms in this question

sexual reproduction