Principles Of Inheritance and Variation for CBSE Class 12 Biology

Basic Requirements

• Class 12 Student

Skills Covered

• Law Of Dominance

• Chromosomal Theory Of Inheritance

Expert Review

Genetics focuses on the principles and mechanisms of heredity and variation. Gregor Johann Mendel is considered to be the father of genetics.

1) The process by which characters pass from parent to progeny is called inheritance. This is the basis of heredity.

2) Variation is how much the progeny differs from the parents.

3) Variations may occur in the morphology, physiology, cytology, or behavior of individuals belonging to the same species.

4) Variation arises due to

5) Reshuffling of genes/chromosomes.

6) Crossing over or recombination

7) Mutation and effect of environment.

Mendel studied the garden pea (Pisum sativum) for seven years to derive the law of inheritance in living organisms.

Mendel chose the pea plant (Pisum sativum) for his experiments because –

1) Peas have many distinct, contrasting characteristics.

2) The pea plant has a short lifespan.

3) Self-pollinating flowers have reproductive whorls enclosed by corollas.

4) It is easy to artificially cross-pollinate pea flowers. The hybrids thus produced were fertile.

Working method: Mendel was also successful because of his meticulous planning and method of work -

1) He examined one character at a time.

2) All available methods were used to prevent cross-pollination by unwanted pollen grains.

3) The results he obtained were analyzed using mathematics and statistics.

4) The contrasting characteristics of garden pea studied by Mendel for his hybridization experiments were seven contrasting Characteristics Studied by Mendel in Pea.