Phenotypic variation (AQA A-level Biology)

This fully-resourced lesson explores how genetic and environmental factors cause phenotypic variation. The engaging PowerPoint and accompanying worksheets have been designed to cover the first part of point 7.3 of the AQA A-level Biology specification which states that students should be able to describe how mutations and meiosis both contribute to genetic variation

Students are challenged at the start of the lesson to recognise the terms phenotype and species from their definitions in order to begin a discussion on the causes of the phenotypic variation within a species. Moving forwards, students will recall that mutations are the primary source of genetic variation and time is taken to look at the effect of gene and chromosome mutations. Just like the majority of parts of this specification point, gene mutations were covered earlier in topic 4 so these tasks act as a prior knowledge check as students have to recognise the different types of gene mutations and explain their effects on the primary structure with reference to the genetic code. These prior knowledge checks are found throughout the lesson and challenge the knowledge of other topics that include photosynthesis, meiosis and inorganic ions. The karyotype of an individual who has Down syndrome is used to introduce chromosome mutations and students will be introduced to the different types, with a focus on non-disjunction. The key events of meiosis that produce variation (crossing over and independent assortment) are explored and students will be given a mathematical formula to use to calculate the number of chromosome combinations in gametes and in the resulting zygote. The final part of the lesson looks at chlorosis and how an environmental factor can prevent the express of a gene.