Question

Test cross in Drosophila or plants involves crossing

• A. The $F_1$ hybrid with a double recessive genotype
• B. Between two genotypes with dominant trait
• C. Between two genotypes with recessive trait
• D. Between two $F_1$ hybrids

Answer 1

The correct option is A The $F_1$ hybrid with a double recessive genotype

In a test cross, the $F_1$ hybrid is crossed with a double recessive genotype. In testcross - the organism with the dominant trait is always crossed with an organism with the recessive trait. If any offspring show the recessive trait, the unknown genotype is heterozygous. If all the offspring have the dominant trait, the unknown genotype is homozygous dominant. Large numbers of offspring are needed for reliable results.

So the correct option is 'The F1 hybrid with a double recessive genotype'.