Genes Interation

[kemmit123]

Hello,

I’m studing about genes interation and get stuck on one of the HW. Can anyone explain how to show it, please?
Thanks a lot. Here is the problem:

* Plant breeders developed two different pure-breeding plant lines that gave no leaves. Each plant was crossed with normal (leafy) pure-bred plants to generate the following phenotypic ratios:

Cross F1 phenotypes F2 phenotypes
Line 1 x leafy All leaves 3:1 leaves : no leaves
Line 2 x leafy All no leaves 3:1 no leaves : leaves
Line 1 x Line 2 All no leaves 13:3 no leaves : leaves

What’s going on here? Why do two apparently similar plant lines produce such different results? For each cross depicted in the table, show the genotypes of all parental, F1, and F2 plants. You will show the results of a total of three crosses.

[kemmit123]

This is the table with 3 columns marked 1, 2 and 3.
1/Cross 2/F1 phenotypes 3/F2 phenotypes
1/Line 1 x leafy 2/All leaves 3/ 3:1 leaves : no leaves
1/Line 2 x leafy 2/All no leaves 3/ 3:1 no leaves : leaves
1/Line 1 x Line 2 2/All no leaves 3/ 13:3 no leaves : leaves

[JackBean]

Hi,

the difference is in whether the novel phenotype is dominant or recesive. The Line 1 is recesive, so when you breed it with leafy plant, it predominats and small plants have leaves. On the other hand, Line 2 is dominant, so even, when you breed it with leafy plant, the new plants will miss leaves. When you cross them together, the small plants will of course miss the leaves.

About the second generation… you get AAbb in first generation. When you cross that, you will get 1:2:1 of homozygous:heterozygous:homozygous. In the first case, as the leaveless alele is recesive, the heterozygotes will be leafy. In the second case, the alele is dominant, so heterozygotes will be leaveless. In the second generation of Line1×Line2, I’m not pretty sure about the result, there will be probably some interaction or something.

[Author]

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