In a species of moth, wing markings are controlled by one gene with two alleles. Moths have either banded wings or plain wings.
A breeder carried out two crosses.
| Cross | Parents | Number of offspring with banded wings | Number of offspring with plain wings |
|---|---|---|---|
| 1 | pure-breeding banded moth crossed with pure-breeding plain moth | 72 | 0 |
| 2 | two banded offspring from cross 1 | 146 | 54 |
Use the results to explain why moths with plain wings appeared in cross 2.
State the expected phenotype ratio if two plain-winged offspring from cross 2 are crossed.
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.