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GCSE Combined Science · key term
An allele expressed in the phenotype even when only one copy is present.
Used by AQA
Specification 4.6.1.4 · Paper 2
Revise: Genetic InheritanceIn a simple dominant–recessive model, a dominant allele is expressed even if only one copy is present. A recessive allele is expressed only when two copies are present, so there is no dominant allele.
Use the same letter for both alleles: a capital for the dominant allele and a lower-case letter for the recessive allele.
A dominant phenotype does not uniquely identify a genotype: the individual could be homozygous dominant or heterozygous.
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