ADVANCED GENETICS PROBLEM Suppose that in peas, the number of seeds in a pod wer

Question

ADVANCED GENETICS PROBLEM

Suppose that in peas, the number of seeds in a pod were governed by the additive polygenic model presented in class (like Nilsson-Ehle’s wheat kernel color). Each adding allele of each gene adds one pea to the pod. The non-adding alleles do not add peas. If a true-breeding strain with 2 peas per pod is mated to a true-breeding strain with 10 peas per pod,

a. what would be the phenotype of the F1 hybrid?

b. how many genes are responsible for the difference between these strains?

c. If the F1 were self-crossed, what portion of the the F2 would have 10 peas per pod?

Explanation / Answer

a- the phenotype of the F1 hybrid will have (2+10)/2 or 6 seeds in the pea.

b- Since each adding allele of each gene adds one pea to the pod & each gene has two copies (pea is diploid), then there are 5 genes concerned which  are responsible for the difference between these strains. In 2 peas per pod plant, any 2 of the alleles out of possible 10 alleles are adding (5 genes, hence 10 alleles); while in 10  peas per pod plant, all the alleles out of possible 10 alleles are adding.

c- In the F1 hybrid, 6 out of the 10 alleles are additive in nature.

The gamete where all the 5 alleles will be additive in nature- probability: (6/10 * 5/9*4/8*3/7*2/6) = 1/42

So, the chance when all the 10 alleles are additive is (1/42 * 1/42) or 1/1764

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