INTRODUCTION
- Genetics-- branch of biology which deals with inheritance and variations of characters from parents to offspring.
- Father of Genetics - Gregor Johann Mendel.
- Inheritance - passing characters from parent to progeny. It is the basis of heredity.
- Variations is the degree by which progeny differs from parents.
- Variations - in the form of physiology, morphology and behavioral characteristics of individual belonging to same species.
- Variations arise due to reshuffling of chromosomes, crossing over, mutations and effect of environment.
MENDEL’S LAW OF INHERITANCE
- Mendel conducted hybridization experiments on garden peas (Pisum sativum) for seven years (1856-1863). On the basis of these experiments he proposed the laws of inheritance.
Steps-
- He selected the characters that has two opposing traits
- concluded his hybridization experiments on 14 true-breeding pea plant varieties.
- True-breeding means a breeding line which has undergone continuous self-pollination and shows stable trait inheritance and expression for many generations.
- Reasons for selecting garden pea plant:
- Easily available on large scale.
- There are many varieties with distinct characteristics.
- They are self-pollinated and can be cross-pollinated easily.
- They have a short life cycle -- can observe many generation very easily.
- Reason for success of Mendel:
- He studied one character at a time.
- He used available techniques to avoid cross pollination by undesirable pollen grains.
- He applied mathematics and statistics to analyze the results obtained from him.
- Mendel selected seven contrasting characters for the experiment.
- By luck, those 7 characters gene are located on different chromosomes.
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