This lecture covers the genetic characteristics of monozygotic twins, focusing on their identical DNA profile and different fingerprints. It also explains the process of paternity testing using microsatellites, including the analysis of loci and parental origin detection. The detection of trisomy 21 (Down syndrome) through microsatellites and postnatal diagnostic methods are discussed, along with pre-implantation diagnostics. The lecture concludes with the impact of maternal age on trisomy 21 incidence and the use of oocyte freezing. Practical examples and scientific techniques are presented throughout the slides.