Question

A purebred plant that produces yellow seeds is crossed with a purebred plant that produces green seeds. The F1 plants have yellow seeds. What is the expected phenotypic ratio of seed color of the offspring of an F1 × F1 cross?

Answer 1

Answer:

3 yellow : 1 green

Explanation:

Let yellow seed trait be represented by Y allele and green seed trait by y allele.

Purebred yellow seed plant = YY

Purebred green seed plant = yy

YY   x    yy  = Yy, Yy, Yy, Yy (all yellow)

This thus means that yellow seed trait is dominant over green seed trait.

F1  x   F1 = Yy  x   Yy, resulting in YY, Yy, Yy, yy offspring.

Since Y is dominant over y,

YY, Yy, Yy = Yellow

yy  = green

Hence, the expected phenotypic ratio of seed color of the offspring of F1 x F1 cross is 3 yellow : 1 green

Answer 2

The yellow seed trait is represented by Y allele and green seed trait is represented by y allele.

Purebred yellow seed plant = YY

Purebred green seed plant = yy

During the crossing to give the F1 generation , the result will be

YY   x    yy  = Yy, Yy, Yy, Yy ( all are heterozygous yellow as yellow  trait is more dominant than green trait)

An F1 x F1 cross will then result in

F1  x   F1 = Yy  x   Yy

               = YY, Yy, Yy, yy

Since Y(yellow) is a dominant trait over y (green),

we have

YY, Yy, Yy = Yellow

and

yy  = green

The expected phenotypic ratio of seed color of the offspring of F1 x F1 cross is therefore 3 yellow  seed : 1 green seed

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