Question

Explain the statement- the law of dominance is not universally applied.

Answer 1

The law of Dominance was put forward by Gregor J Mendel, who is also known as the father of Genetics. It is one of the basic laws included in the Fundamental Law of Inheritance.

Complete answer:
According to the Law of Dominance, the characteristics of an organism are controlled by genes. And within the genes there occurs paired structures known as Alleles. In heterozygous condition, the allele responsible for one character gets masked by another allele and gets expressed instead. The allele, which has the capability of getting expressed in a heterozygous condition is known as the dominant allele, whereas the one that gets masked in presence of a dominant allele is known as the recessive allele.

This law proposed by Mendel is not universally applicable since two other situations were described, where the recessive alleles were found to get expressed even in heterozygous conditions. These conditions are known as incomplete dominance and codominance.

In the case of incomplete dominance, the dominant allele in a heterozygote cannot completely mask the effects of the recessive allele. Thus the phenotype produced would be an intermediate character of both the alleles. A very common example that depicts incomplete dominance is the occurrence of wavy hair.
On the other hand, for co- dominance, both the alleles are expressed equally, even if the alleles are present in heterozygous condition. A perfect example of codominance is seen in the AB blood group of human beings.

Therefore, due to the existence of codominance as well as incomplete dominance, Mendel’s Law of Dominance cannot be accepted universally.

Note: There are three basic laws of inheritance proposed by Mendel. They are the Law of Dominance, Law of segregation as well as Law of Independent Assortment. The Law of segregation states that, during the formation of gametes, the alleles that originally occur in pairs undergo segregation and each gamete would get one allele each. The Law of Independent assortment states that, while combining, the alleles undergo every possible combination.