In a species of ornamental fish called the platyfish (Xiphophorus maculatus), tail-spotting patterns are determined by multiple alleles of a single gene that show codominance.
The table below shows the different tail phenotypes and their genotypes:
| Tail phenotype | Genotypes |
|---|---|
| Moon | TMTM T^M T^M\,TMTM or TMTOT^M T^OTMTO |
| Crescent | TCTC T^C T^C\,TCTC or TCTOT^C T^OTCTO |
| Moon-Crescent | TMTCT^M T^CTMTC |
| Plain | TOTOT^O T^OTOTO |
Explain what is meant by the term codominance.
A breeder crosses a male platyfish with a Moon tail pattern and a female platyfish with a Crescent tail pattern. They produce offspring that have a Plain tail. Use a genetic diagram to show how this is possible. Your diagram should include:
66 exam-style questions on Edexcel IGCSE Biology Inheritance. Each one has a worked solution and a mark scheme showing where the marks go.