In a species of moth, wing markings are controlled by one gene. The allele D D\,D for dark-spotted wings is dominant to the allele d d\,d for wings with no spots.
A female moth with genotype Dd Dd\,Dd is crossed with a male moth with genotype dddddd.
The table shows the phenotypes of their offspring.
| Wing phenotype | Number of offspring |
|---|---|
| dark-spotted wings | 22 |
| wings with no spots | 18 |
Explain how the alleles carried in the parents' gametes produce offspring with both wing phenotypes.
The predicted phenotype ratio for this cross is 1:11:11:1.
Evaluate whether the results support this prediction.
71 exam-style questions on Edexcel GCSE Biology 3.3 Inheritance, covering 3.3.1 Gregor Mendel and the basis of genetics, 3.3.2 Alleles and inherited characteristics, 3.3.3 Monohybrid inheritance, 3.3.4 Determination of sex at fertilisation, 3.3.5 Outcomes from monohybrid crosses, 3.3.6 Inheritance of ABO blood groups, 3.3.7 Inheritance of sex-linked disorders, and 3.3.8 Multiple genes and phenotypic features. Each one has a worked solution and a mark scheme showing where the marks go.