Friday, July 17, 2020

GENETICS

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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