00:01
Hello, this is biology instructor nicole.
00:04
We're going to take a look at your question about genetics with a classic example here of a cross between one tall purple flowered pea plant with yellow seeds.
00:17
So this is one plant here.
00:20
Tall purple flowered tall purple flowered with yellow.
00:29
We're talking about pea plants with yellow seeds.
00:32
And the second is a dwarf white flowered.
00:35
Flowered pea plant with yellow seeds.
00:39
The genotype on the information cards indicate the first plant is heterozygous for height.
00:46
So here are the codes for height.
00:49
So that first one that i use blue for, it's heterozygous for height, but it is tall, so tall is the dominant gene.
00:59
Also heterozygous for flower color, which is capital p for purple and small p for white.
01:11
Purple being dominant, and seed color is also heterozygous.
01:18
So we have capital y for yellow, dominant, and small y for green.
01:26
And the second plant is true breeding.
01:29
So true breeding means homozygous for height.
01:40
So homozygous for height, and it is dwarf.
01:45
So that is going to be small tea, small tea.
01:52
And flower color.
01:55
And the flower color is white flowered.
01:59
So we have two white alleles, so that will be small p, small p, but heterozygous for seed color.
02:08
So that is a capital y, capital y, and a small y.
02:13
What are the genotypes of the parental strains? well, there they are.
02:17
We just did that one.
02:20
Two, in the results of the cross, what percentage of plants would you expect to be phenotypically dominant for all characteristics.
02:32
Well, let's go ahead and do the cross.
02:38
We want the percent dominant for all characteristics.
02:45
Let's see.
02:47
Okay, yep, let's do the cross.
02:49
So when we cross these, the possible combinations we have from, let's do the blue parent here first.
02:58
Remember, we can only have.
02:59
One copy of each chromosome, so one version or one allele.
03:06
So we can have t capital, we can have all dominant.
03:11
We can have dominant, dominant, recessive.
03:17
We can have dominant, recessive, recessive.
03:34
We can also have recessive, dominant, dominant, dominant.
03:39
Dominant.
03:42
We can have recessive, dominant, recessive, and i'm running out of room that way, so i'll have to go over here.
03:50
Recessive, recessive, recessive.
03:54
So these are all the possible combinations from this parent.
04:02
Long straight lines are not as easy to make with this tool as you would think.
04:07
Let's try that again.
04:10
I'm just straight as i can here.
04:17
Okay.
04:18
And then for the second parent, we have recessive, recessive dominant, recessive, recessive, recessive.
04:35
And we have another recessive.
04:42
Let me just make this clear, which are recessive and which are dominant -wise are particularly troublesome with that sometimes.
04:50
So we have recessive, recessive, dominant, and then we'll have recessive -recessive -dominant, and then we'll have recessive -recessive -recessive.
04:55
Recessive and that takes care of these combinations okay and then we'll look to our second allele which is also oh i'm sorry i have one combination left with the first one because we have here to here to here and then we have here to here to here but then we need dominant to recessive to dominant.
05:36
So we have another way to do dominant, recessive, dominant.
05:41
Okay, so far, here's what we have.
05:48
And then starting with this second recessive t, we can do dominant, i'm sorry, recessive, recessive, dominant.
06:01
And then we can have recessive, recessive, recessive.
06:08
And finally, we can have recessive, recessive, recessive dominant.
06:23
Oh, i'm sorry, that was too many.
06:24
Recessive, no, recessive, recessive, dominant.
06:28
And finally, recessive, recessive.
06:31
Recessive.
06:37
I should have nine each, so i am missing a couple.
06:39
So i am going to need more space, which means i may have to redraw this and come back to you.
06:50
But let's not lose what we've done so far.
06:53
All right, so let's just do the combinations possible from each of these parents first.
06:57
So starting with the first blue parent, our first combination is dominant, dominant, dominant.
07:07
And i'm just going to list them first and not put them in the punnet square.
07:12
And then we have dominant, dominant, recessive.
07:21
And then we have dominant, recessive, dominant.
07:28
Excuse me, that one should be a recessive p, dominant.
07:36
Starting with that dominant again, we have dominant, recessive, recessive.
07:49
All right, let's do the, starting with the recessive, t, we have recessive, dominant, dominant, we have recessive, dominant, recessive, let me clear, this is a dominant, capital y.
08:16
And then we have recessive, recessive, recessive, small, small, small.
08:28
So let's just double check that last one, we should have more.
08:34
And i did not erase everything, i realize.
08:37
So let's get rid of these so they don't confuse us.
08:42
I don't need those lines yet.
08:50
So for our small recessive t, we've gotten our recessive, dominant, dominant, recessive, dominant, recessive.
09:08
Recessive, recessive, dominant, recessive, recessive.
09:17
There we go.
09:20
I'm sorry.
09:21
This first one just doesn't even long there.
09:23
There's no such thing as that.
09:25
Okay.
09:28
All right.
09:29
Going to our other parent.
09:30
We have recessive, recessive, dominant.
09:36
Recessive, recessive, precessive, p, dominant, y.
09:44
We have recessive, recessive, recessive, recessive, recessive.
09:51
Recessive, recessive.
09:51
Recessive, recessive.
09:53
Recessive.
09:53
Recessive.
09:53
Recessive.
09:55
And then we have recessive, recessive dominant.
10:03
And then we have recessive, recessive, recessive.
10:14
And before i go any further, i think my mistake i made in the first one that i erase instead of two t dominant t.
10:22
Should have just been dominant t, dominant p, and dominant y, clearly.
10:26
We have to have that combination.
10:28
All right, so we have four combinations from each.
10:31
Yes.
10:31
Oh, we missed one for this recessive down here too.
10:35
So we have recessive, dominant, dominant, recessive, dominant, recessive, recessive, recessive, and we missed recessive, recessive, dominant.
10:49
Okay, almost done.
10:52
Okay, so where did we leave off? oh, recessive, recessive, dominant, recessive, recessive, recessive, recessive, recessive, recessive, recessive, recessive, recessive, recessive, recessive, recessive, recessive, recessive, dominant, and recessive, recessive, recessive, recessive.
11:18
Okay, now we have our parents.
11:21
So you can see what a giant hundred square this shall make.
11:27
But what we're looking for to remind ourselves is the phenotypically dominant for all three of these characters.
11:38
Characteristics.
11:40
So phenotypically dominant means we need one dominant allele for all three.
11:51
So we just need one capital t, one capital p, one capital y.
12:00
So i'm going to draw the square.
12:02
I'll pause for a moment and then we'll come back and do that.
12:04
Okay, so i've go ahead and draw on the pundit square.
12:07
All i've did was put parent one, or let's say parent a, since i already have one there.
12:13
Let's say this is parent a and this is parent b.
12:17
Parent a is here on the horizontal and parent b is down here on the vertical.
12:23
And as you can see, we have an 8 by 8 square.
12:28
So that's going to give us a total of 64 possibilities.
12:33
And we are looking for those that are phenotypically dominant for all characteristics.
12:39
So if we're doing these combinations, for example, we're going to start with our first row and column.
12:48
We have to have a dominant for each one, a t, p, and a y.
12:54
So yes, this one is going to be all dominant.
12:57
Again, we have t, capital t, capital p, capital y, all dominant.
13:01
This one will not count because we have two recessive p's...