HISTORICAL PERSPECTIVES IN GENETICS
Ovists theory: New life is developed entirely from the ovum or ova is responsible for the development of an organism.
Animal culists: they believed that new life is entirely developed from spermatozoa.
Aristotle He believed that life originated from decaying organic matter.This was disapproved by Redi and Spallanzani.
Redi: He proved that fly larvae did not develop when adult flies are prevented from laying the eggs on meat.
Spallanzani: He showed that sealed boiled flask containing heated organic matter did not give rise to development of new organism. He did Artificial insemination in dogs and proved that ova and sperms are responsible for fertilization.
Preformation theory by Bonnet:
Due to faulty microscope he observed a miniature of human body in spermatozoa. Hence he thought that man’s body is already preformed in the spermatozoa.
Theory of epigenesis by Wolf
He disproved the preformation theory by an improved microscope and they found that there were nothing like preformed object and said that sex cells are the structure less liquids. Organs and tissues arise out of the mysterious force and developed to become individuals.
Pangenesis by Darwin:
According to this theory each body cells produce identical copies called Pangens or Gemmules. These are collected first in blood and concentrated in the reproductive organs(Testis/ovaries). These gathered together to form gametes which give rise to new individuals.
Galton and Weismann disproved Pangenesis.
Lamarck proposed the inheritance of acquired character. Acquired characters are inherited together to the next generation. This theory was disproved by Weismann by cutting the rats tail generation after generation upto 20 generations. But all the progenies had tail. He also proposed the germ plasm theory.According to this the germ plasm produces somatoplasm but not vice-versa.
HISTORY
Pythagoras                              -           Vapour theory
Jan Swammerdam                  -           Preformation theory
Charles Bonnet                        -           Encasement theory
Wolf                                        -           Epigenesis
Lamarck                                  -           Inheritance of acquired characters
                                                            Use and disuse theory
Charles Darwin                       -           Evolution theory, Pangenesis
                                                            Natural selection, Origin of species
August Weisemann                 -           Germplasm theory
Hugo de Vries             -           Mutation theory
Johann Gregor Mendel           -           Father of Genetics
William Bateson                      -           coined the word ‘Genetics”
Johannsen                               -           coined the word ‘Gene”
T.H. Morgan                            -           Drosophila melanogaster
                                                            Sex-linked inheritance
Punnet                         -           Linkage between genes
Correns, Hugo de Vries, Tschermark  - rediscovered Mendel’s experiments
Genetics is the science dealt with study of heredity and variation.
Heredity - mechanism of inheritance or transmission of characters from one generation to the next.