19 March 2006

Big Double D's

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?

1 comment:

DesertSurfer said...

Now you see being an 8th grade science teacher I find that to be a riot and exactly something I would say. Of course I find that anytime you can add something a little "naughty" the kids eat it up.

A couple of weeks ago I was talking about meiosis and I asked "where in the male body does meiosis take place?" - naturally one of the boys said quite proudly "THE WEINER!!" and without thinking I said "No, that is pretty much that would be like a UPS truck that makes the deliveries". After several laughs I asked "where does meiosis take place in the female?" and of course somebody yelled out "VAGINA!!" and I figured what the heck...."No, that would be like the loading dock for the UPS truck to back into and deliver his million little packages".

It was actually a bonding experience and they definitely started to pay more attention that day. I am just glad I did not have my admin there doing an observation (of course I would not have changed a word of it).

Great blog....and love the "DD" comment - I never do get tired of homozygous dominant humor - hehehe.