In a species of fish, the allele for patterned fins is dominant to the allele for plain fins. Fish X has patterned fins and is used in two crosses. The results are shown in the table.
| Cross | Parents | Offspring with patterned fins | Offspring with plain fins |
|---|---|---|---|
| 1 | Fish X and a fish with plain fins | 12 | 12 |
| 2 | Fish X and fish Y, which has patterned fins | 18 | 6 |
Explain what the results suggest about the alleles carried by fish X and fish Y, and how plain-finned offspring are produced in cross 2.
186 exam-style questions on OCR GCSE Biology 5.1 Inheritance, covering 5.1.1 The genome, 5.1.2 Environment and phenotype, 5.1.3 Variants and mutations, 5.1.4 How genetic variants influence phenotype, 5.1.5 Asexual and sexual reproduction, 5.1.6 Haploid and diploid, 5.1.7 Meiotic cell division, 5.1.8 Single gene inheritance, 5.1.9 Predicting single gene crosses, 5.1.10 Sex determination, 5.1.11 Multiple gene inheritance, and 5.1.12 Development of our understanding of genetics. Each one has a worked solution and a mark scheme showing where the marks go.