Mendal (1866) proposed that inheritance is controlled by paired germinal units or factors , now called genes. Genes are present in all cells of the body and are transferred to the next generation through gametes .Factors or genes are thus physical basis of Heredity.

1. Course Teacher
Dr. M. Kanimoli Mathivathana
Assistant Professor
Department of Plant Breeding & Genetics
PRESENTED BY
M. THARANI
ID No.: 2017021080
COLLEGE OF AGRICULTURAL TECHNOLOGY
(Affiliated to Tamil Nadu Agricultural University,Coimbatore-3)
((Accredited by Indian Council of Agricultural Research, New Delhi)
Kullapuram (Po), Via Vaigai Dam, Theni - 625 562.

2. PRE MENDALIAN IDEAS ABOUT
HEREDITY

3.  Mendal (1866) proposed that inheritance is controlled by
paired germinal units or factors , now called genes.
 Genes are present in all cells of the body and are
transferred to the next generation through gametes .
 Factors or genes are thus physical basis of Heredity.
MENDAL THEORY

4.  Everyone had a question how a offspring produced from
a parent which is similar to his / her parent or their grand
parents .
 Before the correct definition given by Mendal how the
people or scientist have a idea about heredity [ ie before
1866 ]
 Thus the concept or ideas or theories arise before the
Mendal discovery are said to be Pre – Mendalian
Theories .
HOW PEOPLE THINK EARLIER ???

5.  The Vapour Theory
 The Fluid Theory
 The Theory of Spontaneous Generation
 The Magnetic Power Theory
 The Preformation Theory
 The Theory of Epigenesis
PRE MENDALIAN THEORY :

6.  The Particulate Theory
 The Theory of Acquired characters
 The Theory of Pangenes
 The Germplasm Theory
 Evolution Theory of Inheritance by natural
selection
 Mutation Theory of Inheritance

7. 1. THE VAPOUR THEORY
Greek Philosopher Pythagorus
(600 BC )
 Moist vapour
From body of male
Development of embryo
In uterus of female

8. 2. THE FLUID THEORY
Proposed by the
Greek Philosopher
Empeddes
Each parent produce
fliud ( Semen )
From various parts of the
body
Responsible for
production of an embryo
in the uterus of female .

9. 3. THE THEORY OF SPONTANEOUS
GENERATION
ORIGINATED FROM NON LIVING
ORGANIC ( DECAYING ) MATTER
PRIMITIVE
ORGANISMS
PLANTS
ANIMALS
The Greek Biologist
Aristotle

10. 4. MAGNETIC POWER THEORY
WILLIAM HARVEY ( 1578 – 1657 )
 Experiment made on
deer
Iron by fiction
with a magnet
possess the
magnetic
property
Uterus by fiction
of coitus acquire
some magnetic
power to
concieve an
embryo

11. 5. THE PREFORMATION THEORY
SWAMMERDAN & BONNET
(1720-1793 )
Miniature
human called
Humuncules
present in egg
and sperm
A miniature
human was
preform in
the gametes
Developme
nt of zygote
resulted
only in the
growth of
miniature
human .

12. 6. THE THEORY OF EPIGENESIS
WOLFF ( 1738 – 1794 )
This concept was universally
accepted
That egg or sperm
cells do not
contain miniature
human
They are
undifferentiated
cells - undergo
differentation
after fertilization
– zygote –
development of
adult tissues and
organs

13. 7. THE PARTICULATE THEORY
MAUPERTIUS ( 1698 – 1758 )
semen
Produced by
both parents
During capulation
- form embryo
Each organ of
the embryo –
formed by fusion
Contain many
tiny particles
Two particles
produced by
both the parents

14. 8.THE THEORY OF ACQUIRED
CHARACTERS
Proposed by JEAN BAPTISTE DE
LAMARCK ( 1744 – 1829 )
This theory was disproved
by Weismann
New
character by
individual –
pass on to
progeny
EG : muscle of
man &
children
Weismann
cut tail – 22
generations –
got baby mice
with tail ..

15. 9. THE THEORY OF PANGENES
CHARLES DARWIN
(1809 – 1882 )
 Very small , exact but
individual copies of each
body organ called
gemmules
Transported
by the blood
stream to the
sex organ
Gemmules
are
assembled
in gametes
After
fertilization
Gemmules move
to diff parts –
development of
respective organ
Defective
gemmule
produce
defective organ
In the individual

16. 10.THE GERMPLASM THEORY ( 1887 )
AUGUST WEISMANN
( 1834 – 1917 )
Genes ( ids ) situated in chromosome ( idants )
 Reduction in chromosome no
during the formation of egg and
sperm
 Restore when the egg and sperm
fused
Body tissue
Germplasm
Independent of the body
Somatoplasm

17. 11. EVOLUTIONARY THEORY OF
INHERITANCE BY NATURAL SELECTION
Proposed by CHARLES
DARWIN
BATESON – disagree - he
believed evolution due to large
discontinous variations
 Evolution is due to
natural selection of small
heredity variations
according among
individuals of any species .

18. 12. MUTATION THEORY OF
INHERITANCE ( 1901 )
DE VERIES ( 1848 – 1935 )
 Observed in some plants Oenothera lamarckiana
Introduced term
mutation for these large
discontinous variation in
the genotype

19. REFERENCES
 Krishnan V . Senthil N . Kalaiselvi Senthil .2018 . Third edition ,
Thannanmbikkai Publications , Coimbatore . Pp 1 – 8
 Karvita .b . Ahluwalia , 1996 . Genetics , second edition , New
age international Publishers , New Delhi . Pp 1 – 10
 Roberts .H.F. 1929. Plant Hybridisation before Mendal .
Princeton University .Press .n.J
 Whitehouse , H.L.K . 1973 . Mechanism of Heredity . Third
edition . S.t. Martin’s Press , New York . Pp 8 – 9

20.  Mc Kusick .v. 1969 . Human Genetics . Second edition .
Prentice hall . N.J . Jaipur .
 Dunn .L.C . 1965 . A Short History of Genetics – MC Graw
– hill , NewYork .
 Carlson.E.A.1966. The Gene: A Critical History . Sauders,
Philadelphia .
 Phudan Singh . 2005 . Genetics . First edition . Kalyani
Publishers , New Delhi . Pp 11 – 20 .
 Acquaah george . 2006. Principles of Plant Genetics and
Breeding. Black well Publishers . Pp 4 -6 .