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A common test to find the genotype of a hybrid is by
A
crossing of one F2 progeny with female parent
B
studying the sexual behaviour of F1 progenies
C
crossing of one F1 progeny with male parent
D
crossing of one F2 progeny with male parent
Detailed Solution
An individual showing the dominant phenotype may be homozygous dominant or heterozygous, and this cannot be told from its appearance.
To find the genotype, the hybrid (F1 progeny) is crossed back with one of its parents. Such a cross is called a back cross.
When the F1 hybrid is crossed with the recessive parent, the cross is called a test cross; here the male parent is taken as the recessive parent.
If the hybrid is heterozygous (Rr), the cross Rr x rr gives dominant and recessive offspring in the ratio 1 : 1.
If the individual tested is homozygous dominant (RR), the cross RR x rr gives all dominant offspring.
So from the ratio of the offspring the genotype of the hybrid is known.
Hence the common test is the crossing of one F1 progeny with the male parent, as given in the answer key.