Question

A pure dwarf plant was subjected to x-ray treatment, which mutated them to reach the height of a pure tall plant. This plant was crossed with a hybrid tall. What will be the result of progeny?

Answer 1

Now the alleles of pure dwarf plant if tt
If mutation changed one allele then it would be Tt
Crossing with a hybrid i.e. Tt will produce following progeny:

25%TT, 50%Tt, 25%tt

If mutation changed both alleles it would be TT
Crossing with a hybrid i. e. Tt will produce following progeny:

50%TT, 50%Tt

Answer 2

 In presence of the tall trait, the dwarf trait cannot express itself in the first generation.
(b) In the second generation, however, 25% of the plants reappear as dwarf is homozygous condition (tt).
This indicates that both tallness and dwarfness traits were inherited in $F_{1}$ plants but only tallness trait being the dominant trait could express and dwarf trait being could not recessive

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