Logic Problem:
• You have 4 cards (on next slide) and need to
make as many combinations of them as
possible.
• Each resulting combination must have one
king and one queen.
One of these:
One of these:
How many did you get?
Single Factor Punnetts
• We know how to cross one trait in a Punnett
square.
(ex. Tall plants x short plants)
TT x tt
• What do we do if we want to
cross more than one trait at a
time? (ex. roundness AND pea color)
Bigger Punnett Squares:
•Instead of having only 4
boxes to fill out for 1
trait, now we’ll have 16
boxes for 2 traits.
•How many boxes for 3
traits?
•We need to put the
letters on the top and
side of the Punnett
square, just like a single,
normal one!
•How do we do that?
FOIL (like in math class!)
Simplify this equation: (x + 2)(x + 3)
First, Outer
Inner, Last
Now do the same for
RrYy.
Each result must have one of each letter.
•Each parent’s gametes
must include both
roundness and pea color.
•Hint: Draw a circle
around the genotypes for
roundness and a square
around the genotypes for
color.
•Use arrows to combine
gametes for each box on
the top and side.
•There should be one of
each letter above the top
boxes and one of each on
the left of the boxes.
RrYy x RrYy
Filling out the Punnett
• Complete the cross for RrYy x RrYy.
• Each box should have 4 letters in it…two for
roundness and two for color.
• Find your four possible phenotypes. (round and
yellow, round and green…)
• Determine the genotypes to look for for each
phenotype. (RR/Rr YY/Yy)
• Search through your Punnett to find the numbers
of each.
• Check on page 271 of your textbook to see if you
were correct!
Independent Assortment
• Genes for different traits can segregate (or
assort) independently during the formation of
gametes.
• Just because you got your brown eyes from your mom,
doesn’t mean you also have to get her blond hair!
• This adds to genetic variation in offspring!
Summary of Mendel’s Principles
• Inheritance is determined by genes passed down from
parents to their offspring.
• Some alleles (forms of genes) are dominant while some
are recessive.
• Each parent has two copies of a gene. These genes are
segregated from each other when gametes form.
• Alleles for different genes can segregate independently
from each other.
Homework
• Problems 10, 11, and 13
• Rabbit worksheet