Using FOIL in place of Punnett Squares to determine Genotypes
All students in our school take Biology. They also all take Algebra. Many of these
students struggle with crossing parent genomes to determine the possible genomes and
percentages for offspring. However, these same students have typically taken Algebra by
the time that they reach Biology. One way to differentiate for students learning Punnett
Squares is to allow them to first FOIL the genomes of the parents. The potential
offspring genomes will remain the same, and students are able to determine offspring
from there.
Here is an example of crossing a father with homogenous brown hair (BB) with a mother
that is heterogeneous for brown hair and red hair (Bb):
B
b
B
BB
Bb
B
BB
Bb
Now for students who can apply the FOIL technique to the same set of parents:
BB x Bb
First:
Outer:
Inner:
Last:
BB
Bb
BB
Bb
As you can see, applying this already learned concept can help students to predict
offspring genomes.