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Test cross involves -
A
Crossing between two genotypes with recessive trait
B
Crossing between two F1 hybrids
C
Crossing the F1 hybrid with a double recessive genotype
D
Crossing between two genotypes with dominant trait
Detailed Solution
A test cross is used to find out whether an individual showing the dominant phenotype is homozygous or heterozygous.
In a test cross, the organism with the dominant phenotype (such as the F1 hybrid) is crossed with the homozygous recessive parent instead of being self-crossed.
For a dihybrid, the F1 hybrid (for example RrYy) is crossed with the double recessive genotype (rryy).
Since the recessive parent contributes only recessive alleles, the phenotypes of the offspring directly show the kinds of gametes formed by the hybrid.
A monohybrid test cross gives a 1 : 1 ratio and a dihybrid test cross gives a 1 : 1 : 1 : 1 ratio.
A cross between two F1 hybrids is selfing, which gives the F2 generation.
So a test cross involves crossing the F1 hybrid with a double recessive genotype.
In a test cross, the organism with the dominant phenotype (such as the F1 hybrid) is crossed with the homozygous recessive parent instead of being self-crossed.
For a dihybrid, the F1 hybrid (for example RrYy) is crossed with the double recessive genotype (rryy).
Since the recessive parent contributes only recessive alleles, the phenotypes of the offspring directly show the kinds of gametes formed by the hybrid.
A monohybrid test cross gives a 1 : 1 ratio and a dihybrid test cross gives a 1 : 1 : 1 : 1 ratio.
A cross between two F1 hybrids is selfing, which gives the F2 generation.
So a test cross involves crossing the F1 hybrid with a double recessive genotype.