In a species of lizard, body pattern is controlled by one gene. The allele S S\,S produces a striped pattern and is dominant to the allele sss, which produces a plain pattern.
A striped male is crossed with a plain female. The phenotypes of 80 offspring are shown in the table.
| Offspring phenotype | Number |
|---|---|
| Striped | 38 |
| Plain | 42 |
Explain how the results support the conclusion that the striped male is heterozygous.
The breeder wants to mate this male with a female so that all the offspring are striped.
State the genotype the female must have and explain how this would produce only striped offspring.
For the cross between the male and the plain female, calculate the expected number of plain offspring if they have 150 offspring.
Of the 150 offspring, 68 have a plain pattern.
Explain why this is not the expected number and why recording many more offspring would usually give a proportion closer to the expected value.
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.