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Class 12th Biology 2015 Set1 Delhi Board Paper Solution

Question 13

A teacher wants his/her students to find the genotype of pea plants bearing purple coloured flowers in their school garden. Name and explain the cross that will make it possible.


Purple colour of flowers is a dominant phenotype in pea plants. The genotype of such plants can be determined by a test cross.

Test Cross

When an F1 hybrid is crossed with its homozygous recessive parent, it is known as test cross.

Test cross determines whether the dominant character is coming from homozygous dominant genotype or heterozygous genotype, e.g. purple flower coming from PP or Pw.

In this cross, plant with purple-coloured flowers is crossed with plant with white-coloured flowers, which will always have homozygous recessive genotype.

Thus, the genotype of pea plant bearing purple-coloured flowers in the school garden can be Pw or PP.