Concepts of Heredity

 

2.2 Concepts of Heredity

Heredity : Different Concepts or Principles.

1. Law of continuity of germ plasm-

(i) heredity is determined equally by the mother and the father, i.e. 50% is determined by the mother and 50% by the father,
(ii) the characteristics of grandparents and earlier ancestors exist in fixed quantities as generations progress from one to the next, these ancestral qualities decrease in their influence; for instance, they become successively 1/2, 1/4, 1/8, 1/16,1/32, and so on.

2. Law of regression- Regression refers to the discovery of opposite qualities or traits in the offspring. For instance, the birth of talented offspring to momic or subnormal parents is a case of regression.

3. Law of Mendal - The famous scientist Greger Jhon Mendel conducted many experiments upon rats and beans to study heredity.

(i) Experiments of beans- Mendel planted together an equal number of large and small beans. He found that the beans grew from these plants were large beans. Subsequently, he planted crossbred variety of beans, which gave rise to crossbred beans only. These beans were also large and pure.
(ii) Experiments on rats- Mendel conducted experiments on rats also, and for this pure pose he placed some white and black rats together. Only black rats were bom in this condition. Subsequently, he placed only crossbred rats together and these gave birth to black as well as white rats.