You self-fertilize a pea plant and find that the resultant progeny plants all ma

Question

You self-fertilize a pea plant and find that the resultant progeny plants all make only yellow seeds.

a) Was the original plant most likely a heterozygote or a homozygote for the seed color gene?

b) Is it possible for you to know, from this information alone, whether the yellow seed color allele is a dominant or recessive allele?

A) should be "Heterozygote" and B) should be "No"
However, I was thinking that if A) was a heterozygote, I thought 1/4 of progeny would show recessive trait (something other than yellow). This also led me to answer B) wrong, I thought it would be yes.

Any explanations would be much appreciated!

Explanation / Answer

Self- fertilization involves the union of the female gamete and male gamete from the same individual. The plant was most like a heterozygote. Let me explain this by an example such as By permitting the Fi colored to serve as P2 (second parental generation) and reproduce by self-fertilization to yield F2 progeny. When this is done, and large enough numbers of F2 are obtained from each P2 plant, it is found that among the offspring of every P2 some are colored and some are white. In terms of genetic material, then, these F2 must carry, respectively, C or c Self-fertilization of the round yellow Fi gives offspring which, when counted in sufficiently large numbers, occur in the relative frequencies of 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green. segregation and recombination have occurred for each trait, as revealed in F2 by 12 round : 4 wrinkled and by 12 yellow : 4 green. So, in this case there is also no effect of one trait upon the segregation- recombination behavior of the genetic material for a different trait.

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