Question

The phenotypic ratio in codominance is
A. $$1:2:1$$
B. $$3:1$$
C. $$1:1$$
D. $$2:1:3$$

Answer 1

Hint: When two forms (alleles) of the same gene are expressed in the same living creature, codominance occurs. Both features are present, rather than one being dominant over the other. Codominance is easy to spot in plants and animals having many pigment colours.
When a white-feathered chicken crosses with a black-feathered chicken, the offspring bird has both black and white feathers when it grows up.
When red and white flowers cross in rhododendrons, the result is a bloom with red and white spots.

Complete answer:
Option A: A $$1:2:1$$ ratio is predicted between genotypes and phenotypes of offspring from a cross of two $$F1$$ hybrids heterozygous for a single trait with incomplete dominance.
So option A is not correct.
Option B: A $$3:1$$ Ratio refers to the proportion of phenotypes found in progeny (offspring) produced by mating two heterozygotes who both have one dominant allele and one recessive allele at the genetic locus in question—the progeny on average has one AA genotype.
So option B is not correct.
Option C: A heterozygous state in which both alleles at a gene locus are completely expressed in the phenotype is known as codominance. Neither phenotype is totally dominant in codominance. This is a regular occurrence in the ABO blood type system. The phenotypic ratio is $$1:1$$ when any other blood type (A, B, or AB) is crossed with the O blood group. Both genes are expressed in the same way.
So option C is correct.
Option D: Codominance is a heterozygous situation in which both alleles at a gene locus are fully expressed in the phenotype. In codominance, neither phenotype is completely dominant. In the ABO blood type system, this is a common occurrence. When any other blood type (A, B, or AB) is crossed with the O blood group, the phenotypic ratio is $$1:1$$.Both genes have the same pattern of expression.
So option D is not correct.

So we can say that option C is the correct answer.

Note:
$$F1$$ generation provides the foundation for complete dominance. The $$F1$$ generation of certain organisms differs from both parents. Flower colour in Mirabilis jalapa, Flower colour in Antirrhinum majus, and Feather colour in Andalusian Fowls are examples of incomplete dominance. Correns was the first to notice incomplete dominance in Mirabilis jalapa. Mirabilis has three different sorts of plants based on the colour of its flowers: red, white, and pink.