ObjectiveThe student will be able to:

Find the alleles for a Dihybrid cross using the FOIL method, and the Box

method.

There are two techniques you can use for finding gametes for a Dihybrid Cross.

The best part about it is that they are all the same! Huh? Whaddaya mean?

It’s all about how you write it…Here they are!1)FOIL2)Box Method

Sit back, relax (but make sure to write this down), and I’ll show ya!

The FOIL method is ONLY used when finding the gametes from parents with

two traits. Use the FOIL method to find the

gametes:(RrYy)

(R + r)(Y + y). F tells you to put the FIRST of the

two traits’ alleles together.

RY

(R + r)(Y + y). O tells you to put the OUTER alleles

together.

Ry

(R + r)(Y + y). I tells you to put the INNER alleles

together.

rY

(R + r)(Y + y). L tells you to put the LAST alleles

together.ry

Remember, FOIL reminds you to match up the:

First alleles

Outer alleles

Inner alleles

Last alleles

The third method is the Box Method. This method works for every problem!

Here’s how you do it. • Draw a box. • Write the first set of alleles

on the top and the second set of alleles on the side of a box. It does not matter which goes where.

R r

Y

y

Cross the Alleles as you would in a monohybrid cross.

First alleles:

Outer alleles:

Inner alleles:

Last alleles:

R r

Y

y

RY

Ry

rY

ry

You have 2 techniques. Pick the one you like the best!

RYRyrYry