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Transcript Provided by YouTube:
00:00
Hi and welcome to the AP Biology Lab 7. Genetics of Drosophila podcast. This
00:06
is Mr. Andersen. And in the past we’ve tried doing the fly lab. But with mixed success.
00:11
And so we don’t breed them in class. Usually what ends up happening is we have a bunch
00:17
of escaped fruit flies around the lab. And so we use the virtual fruit fly lab. And so
00:22
where did the fruit fly lab all begin? It’s with this guy, Thomas Hunt Morgan. And so
00:26
he’s in his fly lab right here working on this fruit fly. A fruit fly is great because
00:30
it has pretty simple genome. Reproduces very quickly. And it’s easy to keep in the lab.
00:35
And so, so in this lab let me kind of walk you through the way we use science courseware.org.
00:41
They’ve put together this virtual fly lab. And you can really crank through a bunch of
00:47
fly crosses really really quickly. And the statistics are pretty good. And so first of
00:51
all we should talk a little bit about what makes a female fly different from a male fly.
00:54
Because that’s something on the AP test you need to know. Female flies in general are
00:59
going to be a little bit bigger than male flies. Male flies will also have, you can
01:03
kind of see their rear end is going to be a little bit more rounded than the females
01:07
which is a little bit pointed. And then the big thing that I always see is that the males
01:11
will have these comb like structures called the sex combs. And those sit on the front
01:15
feet. And so that’s one way you can tell the difference. What you do is you just knock
01:19
them out. You anesthetize them. And then they’ll be knocked out and you can count them under
01:24
a microscope. But we’re going to do that all virtually. So let me jump into a browser for
01:29
a second. And so you can login as a guest or you can set up a whole class. But let’s
01:34
login as just a guest. And so in order to do a cross we’ll just do a simple one. You
01:39
click on the computer and then we order flies. And so it asks me do I want to order a female
01:44
fly or male flies? So let’s just order a female fly of the wild type. And so I just click
01:49
on this add to cart. Whenever I’m doing the lab on here I always get lost and I look at
01:54
the big yellow box and it tells me what I should do next. And so if you ever get lost,
01:58
click on that, or look at that. So if I click on add to cart, now it’s added one female.
02:03
And now let’s grab a male of a different, for example let’s try wing size. And so if
02:09
we click on that we’ve got choices. So let’s grab a male that has vestigial wings. And
02:14
so now I’ll buy him. And now I’ve got my cart filled up. So I just say done. Do you want
02:20
to buy these and I say yeah. So I’m going to check out. Alright. So now they arrive
02:25
in the mail like this. I can click on the box and it’s going to put those in a mating
02:29
chamber. And it’s going to put them in an incubator. So now we just simply let them
02:37
go. So two weeks later then we get new flies. The sound effects are kind of annoying and
02:46
you can turn those off. And the animations as well and you can really crank through a
02:50
lot of crosses. So let me grab this. So now we’ve got those crossed. So it was a female
02:56
of the wild type and a male of vestigial wings. We now put them underneath that microscope.
03:01
And then we sort the flies. They would be asleep at this point. And then we’re going
03:04
to sort them out according to gender. And so also it could be any other phenotype. But
03:10
if we look at our two piles here we see we have 543 offspring that are female wild type.
03:15
And then over here we have males of wild type as well. So it looks like we have an equal
03:18
amount of each. Now that would be the F1. So let’s do a F2 cross then. So I’m going
03:23
to look at one of these flies. You can see this is a female. And I’m going to put here
03:26
is a new mating. So she’s added to a new mating jar. Let me zoom out for a second. Now let
03:33
me grab one of the males. And I’m going to add him in a new mating. And then finally
03:40
I’m going to zoom out again. And now I go back to the lab. And you can see that it’s
03:44
added those to a new beaker. And throw them in the incubator. And then let me grab them
03:56
out. And we’ll look at those underneath the microscope. I think that was it. Alright.
04:08
So let’s sort those flies. And now we have different groups. In other words we’ve got,
04:14
it looks like 466 male of the wild type. Whereas we only have 133 females with vestigial. 168
04:23
males vestigial. And then 443 females of the wild type. So this is kind of looking like
04:28
3 to 1 ration that Mendel cross. That famous cross. We could actually send the data at
04:34
this point to the computer and you could do chi-squared analysis. I won’t talk about chi
04:38
squared analysis on here. But I probably do that in a different podcast. But what do you
04:43
do at this point? You want to figure out what’s the inheritance pattern. So it’s looking at
04:46
this point like wild is dominant. Or a better way to say that is that vestigial is recessive.
04:53
So we kind of have that. We’re going to look at is a recessive or is it a dominant trait.
04:57
But then we also have on this matrix two other things. Is it an autosomal gene? Or is it
05:04
going to be sex-linked? And so the next thing I would want to do is I would want to do a
05:08
reciprocal cross. So then I would do a male of the wild type and then a female of that
05:13
vestigial cross. And then do punnett squares and try to figure it out. And so that’s the
05:17
fly lab. Again you can turn off the animations, the sounds and you can really crank through
05:21
a bunch of these crosses really, really quickly. I hope that’s helpful.
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This post was previously published on YouTube.
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Photo credit: Screenshot from video.