Question

F₂ generation in Mendelian cross showed that both genotypic and phenotypic ratios are same as 1 : 2 : 1. It represents a case of ______.

Options

• co-dominance

• dihybrid cross

• monohybrid cross with complete dominance

• monohybrid cross with incomplete dominance

Answer 1

F₂ generation in Mendelian cross showed that both genotypic and phenotypic ratios are same as 1 : 2 : 1. It represents a case of monohybrid cross with incomplete dominance.

Explanation:

Flower colour inheritance in the dog flower (snapdragon or Antirrhinum sp) is a good example of incomplete dominance. The F₁ (Rr) was created in a cross between true breeding red flowered (RR) and true breeding white flowered plants (rr). When the F₁ was self-pollinated, the F₂ had the ratio 1 (RR) red : 2(r) pink : 1 (rr) white. The genotype ratios in this cross were 1 : 2 : 1, as in any Mendelian monohybrid cross, but the phenotypic ratios had shifted from the 3 : 1 dominant recessive ratio to 1 : 2 : 1.