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COURSE Principles of inheritance and variations Lesson1 Basics of genetics Dr. Praveen Kumar Agrawal M.Sc., Ph.D., CSIR NET (JRF). SRF, GATE 21 Years of Pre-medical teaching experience
Term genetics' was first used by William Bateson in 1906. It was derived from a Greek word 'gen', meaning 'to grow into. Therefore, genetics is the science of coming into being' Genetics is the branch of science that deals with heredity and variations. It deals with the principles that govern the origin or birth of a living being. Both heredity and variations play important role in evolution and origin of species (speciation) The most important contribution in the field of Genetics was set by Gregor Johann Mendel. He is therefore, known as Father of Genetics. W. Bateson is regarded as father of modern genetics, T.H. Morgan is called father of experimental gentics. A. Garrod is regarded as father of human genetics.
VARIATIONS Offspring are not the carbon copies of their parents. In fact no two organisms are exactly similar. They have certain remarkable differences. These differences are known as variations. Variations include all changes in morphological, physiological and behavioural characteristics (shape, size, colour, relative position of body organs and habits etc) Variations are the most important basis of organic evolution because without change there can be no possibility of evolution. Kinds of Variations Broadly variations are of two types 1. Somatic and 2. Germinal
1. Somatic or Somatogenic Variations These variations are caused by the effects of environmental factors on the body of the organism. These variations cause local changes in the constitution of the organism and are non-heritable (i.e., these are not transmitted from one generation to the next) These are confined only up to a particular organism and lost with the death of the organism. These variations do not play any significant role from genetical and evolutionary points of view. 2. Germinal or Blastogenic or Genetical Variations e Germinal variations are produced due to the changes in the germplasm of the organisms. Since germ cells participate in gamete production and their fusion (i.e., sexual reproduction), these variations are also called genetical variations because these are inheritable (i.e., passed from parents to the offspring). Only these variations are significant from the evolutionary point of view.
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