A clinic tests 100 people for a disease-associated DNA variant. The variant is present in 20 people, but only 5 of these people currently have the disease.
Which conclusion is supported?
The disease caused the variant to develop in five people.
The disease must develop in the remaining 15 people later.
The variant causes the disease in 20% of all people.
The variant can be present without the disease being present.
40 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.