Question

What is the other name for incomplete dominance?
A. Blending inheritance
B. Co-dominance
C. Pseudo dominance
D. All of the above

Answer 1

Hint: Mendelian ratios are modified in several cases in nature when we consider the interactions among the genes. Such interactions may occur both in allelic as well as non-allelic and give other patterns of inheritance such as incomplete dominance, codominance, multiple allelism, etc.

Complete answer: Incomplete dominance is seen when the dominance of a character over its
a recessive pair is incomplete in nature. It is also called partial dominance or blending inheritance. It
is evident in four O'clock plants (Mirabilis Jalapa) and in Snapdragon( Antirrhinum majus). Here, red-flowered parents are crossed with white-flowered ones and the F1 progenies show pink flowers that are neither red nor white. Here the dominance of one colour over the other is partial or incomplete in nature. In this type of inheritance, both genotypic and phenotypic ratio will be 1:2:1 in the F2 generation. It was first reported in 1903 by Correns in Mirabilis Jalapa. Co-dominance is a condition in which both the alleles of a gene are fully or equally expressed in heterozygotes. Here the recessive alleles are also expressed. Examples are the AB blood group in man. In multiple allelism, a single gene exists in more than two alternative forms. In a normal case, only two alleles will be present. ABO blood grouping in man is an example.
Hence the correct option is A.

Note: A gene that controls more than one phenotype is called a pleiotropic gene. Some genes have the ability to control many phenotypic traits. Phenylketonuria which is an autosomal recessive
disorder in man is an example of pleiotropy. It occurs by a mutation in a single gene that code for
enzyme phenylalanine hydroxylase. It is manifested as mental retardation and reduction in skin and
hair pigmentation.