A genetic screening study includes 90 people who all carry allele R, which is associated with an inherited disorder. Some of these people also carry allele S.
| Alleles carried | Number of people | Number with the disorder |
|---|---|---|
| alleles R and S | 45 | 18 |
| allele R but not allele S | 45 | 9 |
Which conclusion is supported?
Allele S is associated with a lower frequency of the disorder among people carrying allele R.
Allele R occurs only when allele S is also present in the same person.
Allele S is associated with a higher frequency of the disorder among people who do not carry allele R.
Allele S is associated with a higher frequency of the disorder among people carrying allele R.
96 exam-style questions on Edexcel GCSE Biology 3.4 Variation and the Human Genome Project, covering 3.4.1 Causes of variation, 3.4.2 Outcomes of the Human Genome Project, 3.4.3 Genetic variation within a population, and 3.4.4 Effects of genetic mutations on phenotype. Each one has a worked solution and a mark scheme showing where the marks go.