Phenotype and Phenotypic Ratio Calculation:
1. TtRr x ttrr
- In this cross, the genotype of the first parent is heterozygous for two traits (TtRr) while the genotype of the second parent is homozygous recessive for both traits (ttrr).
- The possible gametes for the first parent are TR, Tr, tR, tr, and for the second parent, they are tr.
- The Punnett square for this cross would yield a phenotypic ratio of 1:1 for the heterozygous and homozygous recessive individuals.
2. TtRR X ttrr
- The first parent in this cross is heterozygous for one trait and homozygous dominant for the other (TtRR), while the second parent is homozygous recessive for both traits (ttrr).
- The possible gametes for the first parent are TR and for the second parent, they are tr.
- The Punnett square for this cross would yield a phenotypic ratio of 1:1 for the heterozygous dominant and homozygous recessive individuals.
3. AaBbCC x AaBBCc
- In this cross, both parents are heterozygous for two traits but differ in the third trait.
- The possible gametes for the first parent are ABC, ABc, AbC, Abc, aBC, aBc, abC, abc, and for the second parent, they are ABC and ABc.
- The Punnett square for this cross would yield a phenotypic ratio of 9:3:4 for the different combinations of traits.
Overall, by understanding the genotype of the parents and the principles of Mendelian genetics, we can determine the phenotypes and phenotypic ratios of the offspring in genetic crosses.