This lesson describes the uses and implications of pre-implantation genetic diagnosis, amniocentesis and chorionic villus sampling. The lesson PowerPoint and accompanying worksheets have been primarily designed to cover point 2.15 of the Pearson Edexcel A-level Biology A (Salters Nuffield) specification but regular links are made to the earlier content of topics 1 & 2, and their knowledge of topics including the heart and circulation, monohybrid inheritance and cystic fibrosis are tested.
The lesson begins by challenging them to use this prior knowledge of topic 2 to identify the letters in the abbreviations PGD and CVS. The involvement of IVF to obtain the embryos (or oocytes) is then discussed and a series of exam-style questions are used to get them to understand how this method screens embryos prior to implantation, so that those identified as having genetic diseases or being carriers are not inserted into the female’s uterus. Mark schemes for all of the questions included in this lesson are embedded into the PowerPoint so students can constantly assess their progress.
Moving forwards, Down syndrome (trisomy 21) is used as an example of a chromosomal abnormality that can be tested for using CVS or amniocentesis. Time is taken to describe the key details of both of these procedures so students have a clear understanding of the implications and the invasiveness to the female being tested. The link between amniocentesis and an increased risk of miscarriage is considered and the results of a 2006 study are used to challenge them on their data skills.