Question

The phenotypic ratio of incomplete dominance is
(a) 1:1
(b) 3:1
(c) 1:2:1
(d) 9:3:3:1

Answer 1

Hint: The gene interaction in which none of the two traits of parents are completely seen in the progeny, but an intermediate trait appears, then it is called incomplete dominance. Here none of the two traits dominate one another.

Complete step by step answer:
The ratio of incomplete dominance is 1:2:1.
Incomplete dominance is the form of intermediate inheritance where an allele for a specific trait is not expressed properly over its paired allele. Therefore, it is also known as partial dominance and an example of this is the pink flower appearance in a red color dominant flower.

Additional Information: In the case of incomplete dominance, none of the two characters are completely dominant over one another, therefore, shows an intermediate phenotype that looks like a combination of both. In researches conducted on Mendel's experiments of inheritance, the same type of situation appeared where F1 generation showed variation in the usual pattern and the progeny didn't show characteristics of either parent but appeared as an intermediate progeny. Some examples of incomplete dominance are:
- The mother has straight hair and the father has curly hair, but in that case, the baby will always have wavy hair.
- Carriers of the disease Tay- Sachs exhibit incomplete dominance
- The offsprings of long and short furred rabbits will always have medium fur length.
Therefore, the correct answer is 1:2:1.

Note: Sometimes incomplete dominance is confused with codominance but they are different phenomenons. Let us understand this by taking an example. In the case of codominance, the offspring of a red rose plant and a white rose plant will have flowers with red and white patches, but in incomplete dominance, the whole flower will be pink. Therefore, in codominance, both the alleles are expressed in the phenotype but in incomplete dominance, an intermediate will appear in the F2 generation with a ratio of 1:2:1 of red, white, and spotted.