Q166 / 180 · AIIMS 2001 · Zoology

The ratio in a dihybrid test cross between two individuals is given by

  • A
    $2: 1$
  • B
    $1: 2: 1$
  • C
    $3: 1$
  • Correct answer
    D
    $1: 1: 1: 1$.

Solution

Test cross is a cross to know the genotype of the individual. The individual is crossed with recessive parent. The dihybrid test cross ratio is $1: 1: 1: 1$. The characters under consideration are tall white and dwarf black. Gametes of $\mathrm{TtWw}=\mathrm{TW}, \mathrm{Tw}, \mathrm{tW}, \mathrm{tw}$ Gametes of ttww $=\mathrm{tw}$ Figure
Thus the ratio of $\mathrm{TtWw}:$ Ttww $: \mathrm{ttWw}:$ ttww is $1: 1: 1: 1$.

Hence, the correct answer is option: 'D'.

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