CBSE Class 12-science Answered

In a dihybrid test cross, a plant which produces round and yellow seeds has four possible genotypes- RRYY, RrYY, RRYy and RrYy. To determine the genotype of such a plant, it must be crossed with the one producing wrinkled and green seeds. Such a plant has only one possible genotype, rryy and produces only one type of gamete, namely ry. From the table, it can be seen that the unknown genotypes can be identified from the results of the test cross.

From the above table, it is clear that if equal number of round yellow seeded plants and wrinkled yellow seeded plants are obtained, then the genotype of the parent plant has to be RrYY.