This document summarizes various historical theories of heredity that were proposed before Mendel's rediscovery of the laws of inheritance. These include theories by Pythagoras, Empedocles, Aristotle, Swammerdam and Bonnet, Wolff, and Lamarck. Lamarck proposed the inheritance of acquired characteristics, which was later disproven by Weismann's experiments on rats. Mendel's principles of heredity were rediscovered in 1900 by De Vries, Correns, and Tschermak and included new concepts such as incomplete dominance, co-dominance, and gene interaction.

1. Prepared by-
Uttam Kumar Naik
B.Sc(Ag)
11c/15

2.  Various views are prevelling about the
process of heredity before the rediscovery of
Mendel laws of inheritance.
 Some of these concept are given below-

3.  Given by Pythagorous.
 The body of male produce moist vapour
during coitus which form the body part
of embryo.

4.  Given by Empedocles.
 Each body part produce a fluid .The fluid of
different body part of two parent mix up and
is used in formation of embryo.

5.  Given by Aristole.
The male produce highly purified reproductive blood
containing the nutrient. Female produce reproductive
blood that is impure. The two reproductive blood
coagulate in the body part of the female and form
embryo. Due to purity of reproductive blood the
contribution of character by male is mark.

6.  Given by Swammerdan and Bonnet.
This theory states that a miniature human,
called homunculus,is already present in the egg
and sperm which grow into human being after
formation of zygote

7.  Given by german biologist Wolff.
 The egg and sperm are undifferentiated cell.
The differentation into various organ takes
place only after fertilization in the
zygote.Reulting in the development of adult
tissue.
 It is universally accepted.

8.  Proposed by French Biologist Lamarck.
 A new character acquired by an individual
cell pass into progeny.
 It means if a man develop a strong muscle
by exercise all his children would have
strong muscle.
 It was totally rejected by Weismann.

9.  Given by Weismann.
 He experiment on rat by cutting their tails
and observed the progeny for 22 generation.
In every generation rat progeny continued to
have tails inspite of the fact that the parent
were tailless.
 In this way it discard theory of acquired
character.

10.  The basic principle of hereditary initially
discovered by Mendel in 1866.
 Rediscovered by De Vries, Correns,
Tschermak in 1900.
 These new concept were different from
finding of Mendel.
 These concept are often refered as
“Mendelian Deviation”.

12.  Incomplete dominance.
 Co-dominance
 Multiple alleles
 Linkage
 Lethal gene
 Gene interraction
 Pleiotropic gene effect
 Polygenes
 Environmental effect
 Cytoplasmic effect