Skip to content
IGCSEBiology

Phenotype

Exam-ready definition

The observable features of an organism that result from its genotype and its environment. For example, round seeds or brown eyes.

How this is marked

The word 'observable' (or 'physical features') is what earns the mark. In monohybrid cross answers, give phenotype ratios in words tied to the trait (3 round : 1 wrinkled), not just 3:1.

In an exam answer

Giving a cross outcome: 'The phenotype ratio is 3 tall : 1 short, because the dominant allele is expressed whenever at least one copy is present.'

Full topic guide: Inheritance