This document discusses the principles of inheritance and variation in genetics. It introduces genetics as the study of inheritance and variation of traits from parents to offspring. Gregor Mendel is recognized as the founder of classical genetics, having conducted hybridization experiments with pea plants from 1856-1863 where he identified 7 contrasting traits and proposed the laws of inheritance. Variation arises from processes like crossing over, mutation, and environmental effects on gene expression.

1. PRINCIPLES OF
INHERITANCE
AND VARIATION

2. Genetics
• Genetics is the study of principles and mechanism of inheritance
and variation.
• The science of genetics was pioneered by Gregor Johann Mendel,
who is considered to be the Father of Classical Genetics.

3. • Inheritance is the process by which characters (traits) are passed
on from parent to progeny.
• Continuity of the gene pool is established by the process of
inheritance.

4. • Variation is the degree by which progeny differ from their parents.
• Variation may be in terms of morphology, physiology, cytology
and behavioural traits of individuals belonging to same species.
• Variation arise due to:
• Crossing over (Recombination)
• Mutation
• The environmental effects on gene expression.

5. Mendel’s Law of Inheritance

6. • Gregor Mendel conducted hybridization experiments on garden
pea plant (Pisum sativum) for seven years (1856-1863) and
proposed the three laws of inheritance.
• Mendel was the first to propose that there are factors responsible
for passing on the traits from parent to the offspring.

7. • Selection of pea plant:- The main reasons why Mendel adopted
garden pea plant (Pisum sativum) for experiments were –
• Pea has many distinct contrasting characters.
• Life span of pea plant is short.
• Flowers show self-pollination, reproductive whorls being enclosed
by corolla.
• It is easy to artificially cross-pollinate the pea flowers and the
hybrids thus produced were fertile.

8. 7 pairs of contrasting traits in pea plant studied bymendel