In a species of frog, the allele S S\,S for a stripe on the back is dominant to the allele s s\,s for no stripe.
A breeding programme records the phenotypes of four frogs.
| Frog | Phenotype | Relationship |
|---|---|---|
| A | no stripe | parent of C and D |
| B | stripe | parent of C and D |
| C | no stripe | offspring of A and B |
| D | stripe | offspring of A and B |
Frog D is later crossed with frog E, which has no stripe.
Explain how the breeding record can be used to determine the genotypes of frogs B and D, and predict the probabilities of striped and unstriped offspring from the cross between frogs D and E.
You may use a genetic diagram in your answer.
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.