So since we're dealing with a normal female individual, that means each one of these pairs of chromosomes will consist of two, and that includes chromosome pair 21. And because we're focusing on trisomy 21 in this diagram, I've only drawn this chromosome pair 21. So we have a normal female individual. So after interface, we have the precursor excel, basically replicates each one of these two chromosomes. So remember, we have a normal individual. So we have one of these and one of these.