Punnett Square Practice Problems
Name:_________________________
Directions: Please create a punnett square for each question. Using the data created from
each cross in the punnett square, answer the following questions by providing the answer
behind each question. Each question is worth one point and a completed punnett square
is worth 10pts. 31 points possible.
1. Cross a homozygous dominant Black bull with a homozygous Red Cow. B= black
and b = red
a. What percentage will be black in color?
b. What percentage will be red in color?
c. What are the genotypes in percentage form and phenotypes in ratio form?
2. If Jack Johnson wanted to know how much money he was going to get from his cattle,
he needs to know what color his calves are going to be and if they are horned or polled.
He mated Black Bull polled to a horned Red Cow. B=black, b=red, P=polled, p=horned.
The bull is BBPp and the cow is bbPp
a. What percentage will be black in color?_________
b. What percentage will be red in color?___________
c. What percentage will be black polled?___________
d. What percentage will be red polled?_________
e. What percentage will be red horned?_________
f. What are the genotypes in percentage form and phenotypes in ratio form?
Punnett Square Practice Problems
Name:_________________________
Directions: Please create a punnett square for each question. Using the data created from
each cross in the punnett square, answer the following questions by providing the answer
behind each question. Each question is worth one point and a completed punnett square
is worth 10pts. 31 points possible.
1. Cross a homozygous dominant Black bull with a homozygous Red Cow. B= black
and b = red
a. What percentage will be black in color? 100%
b. What percentage will be red in color?
0%
c. What are the genotypes in percentage form and phenotypes in ratio form?
Genotypes- 100% Bb
Phenotypes-100% black
2. If Jack Johnson wanted to know how much money he was going to get from his cattle,
he needs to know what color his calves are going to be and if they are horned or polled.
He mated Black Bull polled to a horned Red Cow. B=black, b=red, P=polled, p=horned.
The bull is BBPp and the cow is bbPp
a. What percentage will be black in color?___100%______
b. What percentage will be red in color?_____0%______
c. What percentage will be black polled?____25%_______
d. What percentage will be red polled?___0%______
e. What percentage will be red horned?___0%______
f. What are the genotypes in percentage form and phenotypes in ratio form?
Genotypes- 25% BbPP, 50% BbPp, 25% Bbpp. Phenoptypes- 12/16 black
horned, 4/16 black polled
Easter Egg Genetics
Preparation:
Get some packages of plastic Easter Eggs (the kind that split into halves) and some
matching-colored candy, such as gumballs, jelly beans, skittles, etc. Get enough so that
every student gets one or two eggs each. Make a genotype and phenotype chart (for them)
and key (for you) to accompany them. For example: (the letters represent the color of
HALF of the Easter egg)
Chart:
PP=purple
pp=pink
Pp=orange
BB=blue
bb=yellow
Bb=green
[An egg may have both halves purple (PP * PP), or, it may be orange and pink (Pp * pp)]
Key:
purple x purple purple x purple (PP x PP)= all PP (purple)
purple x pink (PP x pp)= all Pp (orange)
pink x pink (pp x pp)= all pp (pink)
orange x orange (Pp x Pp)= 1 purple (PP), 2 orange (Pp) and 1 pink (pp)
orange x purple (Pp x PP)= 2 purple (PP) and 2 orange (Pp)
orange x pink (Pp x pp)= 2 orange (Pp) and 2 pink (pp)
etc. (for any other color combinations)
The students will fill the eggs according to your key. For example, a (phenotypically) half
pink and half purple egg would represent the genotypes PP x pp, each half of the egg
representing the genetic input of one parent. Then, students would do a Punnett Square to
determine what offspring would be possible from such a cross. The Punnett Square
calculation reveals that all of the offspring would be genotypically Pp, or phenotypically
orange. The candies inside would be appropriate colors to match the results of their
Punnett Square so that they could check themselves to see if their calculations were
correct. The students then get to eat the candy.
The Activity:
Introduce the concepts of dominant and recessive alleles, Punnett Squares, etc. Pass out
an egg that you have prepared to each student. Put a chart up on the board or overhead
that indicates what trait is represented by the color of each half of the egg they are
holding. Then, students examine their respective eggs, figure out the genotypes of their
"parent" eggs, and do a Punnett Square to determine what “color” offspring would be
possible from such a cross. The candies inside would be appropriate colors to match the
results of their Punnett Square so that they could check themselves to see if their
calculations were correct.