AQA GCSE Combined Science Trilogy · 8464
Specification 4.6.1.5 · Paper 2
Revise: Inherited DisordersA dominant allele is expressed when one copy is present; a recessive allele is expressed only when two copies are present.
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GCSE Combined Science · key term
An allele expressed in the phenotype when one copy is present.
Used by AQA and Edexcel
Specification 4.6.1.5 · Paper 2
Revise: Inherited DisordersA dominant allele is expressed when one copy is present; a recessive allele is expressed only when two copies are present.
Paper 1, Paper 2
An allele expressed in the phenotype when one copy is present, including in a heterozygous individual.
Revise: Alleles and inheritance patternsA dominant allele is expressed when just one copy is present. A recessive allele is expressed only when both copies are recessive in this model.
State that cystic fibrosis is a disorder of cell membranes caused by a recessive allele, whereas polydactyly means extra fingers or toes and is caused by a dominant allele.
Use the same letter for both alleles of a gene, with a capital for the dominant allele and a lower-case letter for the recessive allele. Define your symbols.
Use the same letter for both alleles: a capital for the dominant allele and lower case for the recessive allele. Define what each represents.
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