Question

A homozygous plant having round (R) and yellow (Y) seeds is crossed with another homozygous plant having wrinkled (r) and green (y) seeds. Answer the following questions:

1. Give the genotype of the F₁ generation.
2. Mention the phenotype of the F₁ offspring.
3. Give the possible combinations of gametes that can be obtained from F₁ hybrids.
4. Give the dihybrid phenotypic ratio and the phenotype of the offspring of the F₂ generation when two plants of F₁ generation are crossed.
5. Name and state the law which explains the dihybrid phenotypic ratio.

Answer 1

1. RrYy, the genotype of the F₁ generation, will arise from the homozygous dominant traits (RRYY) of one parent mixed with the homozygous recessive traits (rryy).
2. Round, yellow seeds are the main feature of the F₁ progeny's phenotype.
3. Gametes from the F₁ generation will have the alleles R, r, Y, and y in different combinations, such as RY, Ry, rY, and ry.
4. In the F₂ generation, the dihybrid phenotypic ratio is 9 : 3 : 3 : 1. The following are the phenotypes of the F2 generation's children:
   Round and yellow seeds (RRYY, RRYy, RrYy) 9/16 will have.
   Round and green seeds (RRyy, Rryy) will be found on 3/16.
   3/16 will have yellow and wrinkled seeds (rrYy, rrYz).
   1/16 will have ry, or wrinkled, green seeds.
5. Mendel's law of independent assortment holds that individual traits arrange themselves separately during gamete development when two or more characters are inherited. Therefore, every allele in a pair separates independently and every gamete created carries one allele of that trait.