You decide to study the genetics of a hypothetical...

You decide to study the genetics of a hypothetical houseplant. You are studying two traits. You may assume that each trait is the result of a single gene. Leaf shape: broad or narrow Stem height: long or short You are given several dozen seeds from the mating of two different true-breeding parent plants, but you do not know the phenotypes of the parents. You grow the seeds into adult plants and find that they all have the same phenotype: broad leaves, long stems. Call these plants the F1 generation. Now, you allow the F1 plants to crosspollinate. You collect seeds, grow them into adult plants, and count phenotypes. Call these plants the F2 generation. Your results: F2 phenotypes Broad leaves, long stem 28 Broad leaves, short stem 10 Die as seedlings 9 Narrow leaves, short stem 3 a) Which leaf phenotype is dominant? Which stem phenotype is dominant? b) What must be the genotype of the F1 plants? Be sure to define your allele designations. c) What phenotype class is missing in the F2 generation? Provide a plausible explanation as to why this class is missing. d) What must have been the phenotype and genotype of the two parents of your original seeds?

Transcript

00:01 Now, a hypothetical situation is provided to us in this question where we are studying one of the house plant.

00:08 We are studying a house plant and there are few statements or number that are already given to us.

00:15 First of all, we will see the characteristics that have been given.

00:18 So when we talk about the leaf shape for the house plant, it could be broad or narrow.

00:26 And the other thing that we have studied here is the stem height.

00:34 So here it could be long or it could be short.

00:43 Now moving further, we have been given a few of the results.

00:47 Few results are already been provided to us and they are that in the f2 generation, we have broad leaves and long stem 28.

00:58 So there are 28 broad leaf and long stem.

01:07 While if i talk about the next data, it is 10 broad leaf but short stem.

01:17 Then few of them die as seedling.

01:23 Few of them die as a seedling and the number is 9.

01:28 And finally, you have 3 with narrow leaves and short stem.

01:40 Now here you have been asked which leaf phenotype is dominant and which stem phenotype is dominant.

01:47 So now here the very first question we need to tell about the dominant trait.

01:55 So now when we look on to this, when we are talking about the dominant for the leaf, it will be broad.

02:04 As we can see, the number is high when we look for the results in f2 generation that is broad leaf and long shoot is 28.

02:16 So the number is high.

02:17 Therefore, we could say that leaf dominant is broad leaf and for the stem, it is tall stem.

02:26 Tall stem.

02:30 The next is that we need to, so here it is the dominant ones, broad and tall.

02:37 Now moving on to the next one, we have to give the genotype of the plant in f1 generation.

02:42 If we look properly, then here in f2 generation, there is a heterozygosity being displayed very clearly.

02:50 That means in f1 generation, there was a hybrid condition.

02:54 So we will say it is lltt where this ll is capital l and small l, tt is capital t and small t representing two different alleles.

03:07 Then we can say that here it was a heterozygous f1 generation plant.

03:13 Now see part of the question, the phenotype that is missing from the f2 is.

03:17 Now which is the phenotype that is missing? as you can see, we have broad and long, broad and short, narrow and short, but there is one which is left and that is narrow leaf, narrow leaf, but long stem.

03:37 So this phenotype was not present or is left...

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