Genetic diversity (AQA A-level Biology)

This fully-resourced lesson describes genetic diversity as the number of genes in a population and explains how this is increased by polymorphic gene loci. The engaging PowerPoint and accompanying differentiated resources have been primarily designed to cover the first part of point 4.4 of the AQA A-level Biology specification but also introduces inheritance and codominance so that students are prepared for these sub-topics when covering topic 7 in the following year.

In order to understand that 2 or more alleles can be found at a gene loci, students need to be confident with genetic terminology, so the start of the lesson focuses on key terms including gene, locus, allele, recessive, genotype and phenotype. A number of these will have been met at GCSE, as well as during the earlier lessons in topic 4 when considering meiosis, so a quick quiz competition is used to check on their recall of the meanings of these terms. The CFTR gene is then used as an example to demonstrate how 2 alleles results in 2 different phenotypes and therefore genetic diversity. Moving forwards, students will discover that more than 2 alleles can be found at a locus and they are challenged to work out genotypes and phenotypes for a loci with 3 alleles (shell colour in snails) and 4 alleles (coat colour in rabbits). At this point, the students are introduced to codominance and again they are challenged to apply their understanding to a new situation by working out the number of phenotypes in the inheritance of blood groups. The lesson concludes with a brief consideration of the HLA gene loci, which is the most polymorphic loci in the human genome, and students are challenged to consider how this sheer number of alleles can affect the chances of tissue matches in organ transplantation.