Question

A pea plant purebred to produce round yellow peas is crossed with a plant purebred to produce wrinkled green peas. Round pea shape is dominant to wrinkled, and yellow pea color is dominant to green. Members of the resulting F1 generation are then crossed to produce an F2 generation, as shown in the figure. On average, what fraction of the F2 generation will display both recessive traits?      

Answer 1

Answer:

1 out of 16 or 1/16

Explanation:

Let:

R = Round seed      r = wrinkled seed

Y = Yellow seed     y = green seed

Starting from the parent generation or the P generation, the genotype of the parents would be:

RRYY x rryy

This is because the cross is between a parents that are "purebred" for specific traits. This means that the parents are homozygous for the traits which in genotype form is represented by either two capital letters or two lower case letters.

Attached is the F1 generation results between a cross between the P generation.

As you can see the genotype of all the offsprings is RrYy.

Now also below is the cross between the F1 generation offsprings.

For recessive traits, it is only expressed when the dominant gene is not in the genotype, or in other words, the genotype is all in small letters. Since we are looking at two traits, you need to look for how many squares out of the total have all lowercase letters.

There is only 1 rryy out of the 16 predictions. So the answer would be 1/16.