Question

In a monohybrid cross male plants having red coloured flowers were crossed with the females
plants with white coloured flowers. It was seen that in the first generation (F) all the offspring
bore red coloured flowers. However, when 56 such plants were self-crossed, it was observed in
the second generation (F2), that 39 plants bore red flowers and only 13 had white flowers.
(i) What are the genotypes of R and F2 progeny?
(ii) What inference could be drawn from the above data?
(iii) What would be the genotypic ratio of the progeny if the Fi males were crossed with paren
females?​

Answer 1

On crossing red and white flower only red colour flower appeared in the F1 generation. But the white colour flower again appear in the F2 generation which is raised out of the F1 individuals only. Mendel reasoned that there is a factor of each and every character. Accordingly, there has to be one factor (R) for red flower and other one factor (r) for white flower. In case, an organism possess only one copy of the gene then the possibility of reappearance of white flower in the F2 generation of the given cross is not there. Also the ratio (3 : 1 of red and white) indicates that each organism must possess two copies of a particular gene.

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