Assumption-2 :

During reproduction one 'factor' from each parent is taken to form a new pair in the progeny.

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Assumption-3 :

One of these will always dominate the other if mixed together. The trait expressed in F1 generation is called dominant. While the other which did not express in F1 is called recessive.

Assume that 'Y' (the one causing yellow colour) is a dominating 'factor'. That means if 'Y' and 'y' come together 'Y' will dominate. Then the pea seeds will be always yellow in colour.

From assumption-2, the breed after cross pollination will have one factor from pure breed yellow (Y) and one from the pure breed green (y).

That is, all the peas will have the paired factor 'Yy' and by assumption-3 all the peas will be Yellow as 'Y' factor is dominant

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All the pea plants are yellow (F1-Generation). The trait expressed in F1 is dominant, unexpressed is recessive. This is the law of dominance.

Self pollination in F1-Generation

On self pollinating these peas (ones with Yy factor), the new breed have any combinations of ‘Y’ and 'y'

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F-2 Genaration

So in this heap we will get approximately equal number of YY, Yy, yY and yy peas. But any pea that has a Y factor will be yellow. Any pea that has both yy will be green. Since all combinations are equally likely:

1. YY will be approximately 25% and is yellow.

2. yY will be approximately 25% and is yellow, Yy will be approximately 25 % and is yellow

3. yy will be approximately 25% and is green.

Some seeds appear yellow in colour in F1 generation. When these


pg.no.173
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