Principles of Inheritance and Variation Class 12 Notes

Heredity is a process of transferring traits from parents to their offspring’s either through the asexual reproduction or sexual reproduction. These traits are present on the chromosomes in the form of genes and these genes are the characters which may be similar to one of its two parents.

Gregor Johann Mendel- who is known as the Father of Genetics was the first scientist to conduct experiments on Heredity, Inheritance and Variations.

Law of Inheritance or Mendel’s Laws of Inheritance

Inheritance is the process by which traits are transferred from parent to its progeny. It is the basis of heredity. Variation is the degree by which progeny differ

from their parents and usually occurs due to the reshuffling of a gene or a

chromosomes, mutations, crossing over and other environmental effects.

According to Mendel’s experiments on garden pea plants for seven years.

Plant Height

F1 Generation TALL TALL

In his experiments, he crossed both the tall and dwarf pea plants to study the inheritance of one gene. He observed that all the F1 progeny plants were tall, as one of its parents and none were dwarf. He made similar observations for the other pairs of traits and found that the F1 always resemble either one of the parents and that the trait of the other parent was not seen in them.

Mendel then self-pollinated the tall F1 plants and was surprised to found that in the F2 generation some of the offspring were dwarf, the character that was not seen in the F1 generation was now expressed. According to his observations, the proportion of plants that were dwarf were 1:4 of the F2 plants while 3:4 of the F2 plants were tall. The tall and dwarf traits were identical to their parental type.

Few Important Questions

  • What is point mutation? Give one example
  • Define Principles of Inheritance and Variation?
  • Differentiate between Homozygous and Heterozygous?
  • List out the three main laws proposed by Gregor Johann Mendel?

Learn more about Heredity, Law of Inheritance, chromosomes, and genes from the topics given below:

Practise This Question

Apomixis leads to polyembryony.