Question

Mendel crossed peas having round seeds and yellow cotyledons (seed leaves) with peas having wrinkled seeds and green cotyledons. All the F1 plants had round seeds with yellow cotyledons. Diagram this cross through the F2 generation, using both the Punnett square and forked-line, or branch diagram, methods.

Answer 1

Let:

Y = Yellow R = Round

y = green r = Wrinkled

If you look at the F1 generation, all the plants are round and yellow, so these are the dominant traits and each offspring is heterozygous for both traits. The cross for the F2 generation would then be:

YyRr x YyRr

In a Punnett it would look like the attached picture.

For the forked-line diagram, first you will need to know the gentypes and ratio of each trait in a monohybrid cross. Select one trait, and then branch each gentype to the next trait, linking it with each possible genotype combination of the monohybrid cross.

Attached is a picture of the Forked Branch diagram for this cross.