Scientists compare the DNA of 200 healthy people. They find many differences in DNA sequence, although the people have similar observable characteristics.
Which statement best explains this finding?
Healthy people cannot possess any mutations in their DNA.
Similar phenotypes show that all DNA sequences are identical.
Many genetic differences have no effect on observable phenotype.
Every genetic difference produces a large change in phenotype.
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.