Answer:
Phenotype ratio= 3: 1
Genotype ratio = 1:2:1
Explanation:
According to the punnet square, the cross involves a single gene D and it is between two heterozygous parents Dd i.e. parents with a combination of different alleles because they produced gametes D and d.
This is similar Mendels experiment with the height of pea plants. So let's say that allele D is the dominant allele while allele d is the recessive allele i.e. allele D is capable of masking the expression of allele d in a heterozygous state.
Hence, in a cross between two heterozygous parents (Dd), four possible offsprings will result as seen in the image: DD, Dd, Dd, and dd.
Because (D) will mask the expression of (d), it (D) will be expressed in the heterozygous state (Dd). Therefore, DD, Dd, and Dd
offsprings will have the same dominant phenotype while dd offspring will have a recessive phenotype. This gives a phenotypic ratio of 3:1
Observing the offsprings closely, they possess different genetic make-up. 1 offspring has a DD genotype, 2 have Dd genotype, and 1 has a dd genotype.
DD is said to be homozygous dominant i.e. it contains the same dominant alleles
Dd is heterozygous dominant i.e. it contains different alleles but still exhibits a dominant trait
dd is homozygous recessive i.e. it contains the same recessive alleles.
Hence, based on the difference in the genetic make-up of the offsprings, they have a genotypic ratio of 1:2:1 .
