Euphorbia cyathia are typically seen as flowers but are...

Euphorbia cyathia are typically seen as flowers, but are actually: simple flowers that lack sex parts, but instead reproduce asexually through apomixis composite inflorescences composed of numerous complete flowers that each have different numbers of floral components composite inflorescences composed of numerous incomplete flowers that each only exhibit one floral component specialized leaves that mimic flowers for the purposes of tricking pollinators to visit their carnivorous traps

Transcript

00:01 For this question, we have three different types of phenotypes.

00:03 We have a big s for single.

00:07 They use a big d for double, and they use s -d for a super double.

00:19 So the key to this is looking at the first cross they conduct, where they are crossing a pure s and a pure d.

00:28 So the offspring from this cross results in all s organisms.

00:36 So they're all going to have that single flower.

00:39 This indicates typically some sort of homozygous, dominant and homozygous recessive nature.

00:47 And since s occurs, you can figure that your pure s is going to be a dominant to the d trait, which is going to be recessive.

01:00 So with this in mind, i'm going to use a big s for the single genotype, and i'll use little s's for the recessive or double genotype.

01:15 So if we move down the line, for cross 2, we have f1 cross f1.

01:23 So this is going to be this all -s organism that came out of this first cross.

01:29 So for this pure s, we could imagine this would be our homozygous dominant, and pure d would be a homozygous recessive.

01:38 So the offspring we should get from this should all be heterozygous.

01:43 So if we do a cross of two heterozygous individuals, big s little s cross big s little s, we should get about a 3 to 1 ratio of dominant to recessive, because about 25 % will be homozygous dominant, 50 % will be heterozygous, but will display the dominant phenotype, and about 25 % will be homozygous recessive.

02:11 And this matches up to the numbers that we're given of about 78 to 27, which is about a 3 to 1 ratio.

02:21 So this fits that our single and double phenotypes have this dominant and recessive relationship.

02:31 So from here, we have to look at the effects of this super double population.

02:37 So for cross 3, we have a pure d, so little s, little s cross this super double.

02:45 And the results we get out of this is we're going to have about a one -to -one ratio of the super -double to the super -double to the d.

02:58 Population.

03:00 So how this works is i'm going to use an x for this super double population.

03:08 So if we imagine we have a large x and a little x and that only this large x phenotype is going to be displayed, the cross result of this third cross would be a big x, little s, about 50 % of the time, and about little x, little s, 50 % of the time.

03:31 And if we expect only the big x to display this super double, and the little x to not, we would have this proper one -to -one ratio...

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