Hi and welcome to the AP Biology Lab 7. Genetics of Drosophila podcast. This
is Mr. Andersen. And in the past we've tried doing the fly lab. But with mixed success.
And so we don't breed them in class. Usually what ends up happening is we have a bunch
of escaped fruit flies around the lab. And so we use the virtual fruit fly lab. And so
where did the fruit fly lab all begin? It's with this guy, Thomas Hunt Morgan. And so
he's in his fly lab right here working on this fruit fly. A fruit fly is great because
it has pretty simple genome. Reproduces very quickly. And it's easy to keep in the lab.
And so, so in this lab let me kind of walk you through the way we use science courseware.org.
They've put together this virtual fly lab. And you can really crank through a bunch of
fly crosses really really quickly. And the statistics are pretty good. And so first of
all we should talk a little bit about what makes a female fly different from a male fly.
Because that's something on the AP test you need to know. Female flies in general are
going to be a little bit bigger than male flies. Male flies will also have, you can
kind of see their rear end is going to be a little bit more rounded than the females
which is a little bit pointed. And then the big thing that I always see is that the males
will have these comb like structures called the sex combs. And those sit on the front
feet. And so that's one way you can tell the difference. What you do is you just knock
them out. You anesthetize them. And then they'll be knocked out and you can count them under
a microscope. But we're going to do that all virtually. So let me jump into a browser for
a second. And so you can login as a guest or you can set up a whole class. But let's
login as just a guest. And so in order to do a cross we'll just do a simple one. You
click on the computer and then we order flies. And so it asks me do I want to order a female
fly or male flies? So let's just order a female fly of the wild type. And so I just click
on this add to cart. Whenever I'm doing the lab on here I always get lost and I look at
the big yellow box and it tells me what I should do next. And so if you ever get lost,
click on that, or look at that. So if I click on add to cart, now it's added one female.
And now let's grab a male of a different, for example let's try wing size. And so if
we click on that we've got choices. So let's grab a male that has vestigial wings. And
so now I'll buy him. And now I've got my cart filled up. So I just say done. Do you want
to buy these and I say yeah. So I'm going to check out. Alright. So now they arrive
in the mail like this. I can click on the box and it's going to put those in a mating
chamber. And it's going to put them in an incubator. So now we just simply let them
go. So two weeks later then we get new flies. The sound effects are kind of annoying and
you can turn those off. And the animations as well and you can really crank through a
lot of crosses. So let me grab this. So now we've got those crossed. So it was a female
of the wild type and a male of vestigial wings. We now put them underneath that microscope.
And then we sort the flies. They would be asleep at this point. And then we're going
to sort them out according to gender. And so also it could be any other phenotype. But
if we look at our two piles here we see we have 543 offspring that are female wild type.
And then over here we have males of wild type as well. So it looks like we have an equal
amount of each. Now that would be the F1. So let's do a F2 cross then. So I'm going
to look at one of these flies. You can see this is a female. And I'm going to put here
is a new mating. So she's added to a new mating jar. Let me zoom out for a second. Now let
me grab one of the males. And I'm going to add him in a new mating. And then finally
I'm going to zoom out again. And now I go back to the lab. And you can see that it's
added those to a new beaker. And throw them in the incubator. And then let me grab them
out. And we'll look at those underneath the microscope. I think that was it. Alright.
So let's sort those flies. And now we have different groups. In other words we've got,
it looks like 466 male of the wild type. Whereas we only have 133 females with vestigial. 168
males vestigial. And then 443 females of the wild type. So this is kind of looking like
3 to 1 ration that Mendel cross. That famous cross. We could actually send the data at
this point to the computer and you could do chi-squared analysis. I won't talk about chi
squared analysis on here. But I probably do that in a different podcast. But what do you
do at this point? You want to figure out what's the inheritance pattern. So it's looking at
this point like wild is dominant. Or a better way to say that is that vestigial is recessive.
So we kind of have that. We're going to look at is a recessive or is it a dominant trait.
But then we also have on this matrix two other things. Is it an autosomal gene? Or is it
going to be sex-linked? And so the next thing I would want to do is I would want to do a
reciprocal cross. So then I would do a male of the wild type and then a female of that
vestigial cross. And then do punnett squares and try to figure it out. And so that's the
fly lab. Again you can turn off the animations, the sounds and you can really crank through
a bunch of these crosses really, really quickly. I hope that's helpful.