Class notes biology BIOLOGY Simplified NCERT Class XII

Principles of Inheritance and variation


INHERITANCE :

Process by with character / traits transfer from parent to offspring

VARITES :
Degree by which character differ from parent and offspring .


MENDLE’S LAWS OF INHERITANCE

i. GREGOR MENDEL : Proposed the law of inheritance

ii. He conducted hybridisation experiment on garden peas almost 7 years

iii. He is the one , first used partten of statistic analysis and mathematical
logic in biology .

iv. His experiment had an :
a. large sampling size
b. Continious experiments on generation
c. Oppossing traits ..eg: tall / drawf plants
d. Artificial pollination - self polli / cross polli
e. He selected 14 true - breeding pea

CONTRASTING TRAITS STIDIED BY MENDEL IN PEA
Stem height Tall / dwarf
Flower colour Violet / white
Flower position Axial / terminal
Pod shape Inflated / constricted
Pod shape colour Green / yellow
Seed shape Round / wrinkled
Seed colour Yellow / green

, Vi . two in chromosome no . 1, three in chromosome no . 4 , one in
chromosome no.5 and one in chromosome no. 7 - ARRANGEMRNT
OF MEDEL’S SELECTED 7 TRAITS ON 4 CHROMOSOME

Vii . MENDEL CHOOSED PEA PLANT BECAUSE :

a. The flower of this plant are bisexual.
b. They are self pollinating , self and cross pollination can easily be
performed
c. The diff physical characteristics were easy to recognize and study
d. They have short life span
e. Available on large scale
f. There are many varieties with distinct characteristics