My AP kids are knee-deep into our genetics unit at the moment. We've been talking about different ways to track traits and make predictions about what might happen from different parental combinations.
Last week, we started talking about pedigrees: charts of ancestry like the one shown below. Circles represent females; males are shown by using a square. Circles and squares that are coloured in are for whatever trait is being tracked by the chart. Older generations are at the top. Lines between two people represent parents. Lines connected above are for siblings.
Anyway, the kids were looking at a practice pedigree on Deaf-Mutism. They were supposed to write the genotypes (gene combinations) for each person on the chart. An uppercase "D" was for a normal gene and a lowercase "d" for the deaf-mute trait. For this particular trait, this means that every blackened circle and square meant that the gene combo was "dd." Anything blank had at least one uppercase D.
A few minutes after working through the pedigree and assigning D/d's to people, a girl looked up and asked, "How do you get big double D's?"
I gave her the first answer that came to mind: "implants."
Never a dull moment in the classroom, is there?