Page 9 - Lesson Notes- Principle of inheritance & Variation
P. 9
Inheritance of Two genes (Dihybrid Cross)
A cross made to study simultaneous inheritance of two pairs of mendelian factors of genes.
Law of independent Assortment – The law states that ‘when two pairs of traits are combined
in a hybrid, segregation of one pair of characters is independent of the other pair of
characters’.In Dihybrid cross two new combinations, round green & wrinkled yellow are
formed due to independent assortment of traits for seed shape i.e round, wrinkled and seed
color i.e , yellow and green.
The ratio of 9:3:3:1 can be derived as a combination series of 3 yellow: 1 green, with 3 round :
1 wrinkled. This derivation can be written as follows: (3 Round : 1 Wrinkled) (3 Yellow : 1
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