Name: _________________________________
Date: _________________
Period: ______
How is probability related to inheritance?
The Punnett Square is…
(Please start on page 138 in your book.)
_____________________________________________________________
_____________________________________________________________
How can a Punnett Square be used to make predictions about offspring?
_____________________________________________________________
_____________________________________________________________
How can a pedigree trace a trait throughout generations?
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
PUNNETT SQUARE
MOM
Genotype: ______
Phenotype: __________________
DAD
Genotype: ______
Phenotype: __________________
Name: _________________________________
Date: _________________
Period: ______
Practice Problems!
Set up the square for each of the crosses listed below. The trait being studied is round seeds
(dominant) and wrinkled seeds (recessive). Remember to show all work!
1. Rr x rr
What percentage of the offspring will be round? ___________
2. Rr x Rr
What percentage of the offspring will be round? ___________
3. RR x Rr
What percentage of the offspring will be round? ___________
Name: _________________________________
4. A TT (tall) plant is crossed with a tt
(short plant).
Date: _________________
Period: ______
7. A homozygous round seeded plant
is crossed with a homozygous
wrinkled seeded plant.
What are the genotypes of the parents?
________ x ________
What % of the offspring will be tall? ________
5. A Tt plant is crossed with a Tt plant.
What % of the offspring will be homozygous?
________
8. In pea plants purple flowers are
dominant to white flowers.
What % of the offspring will be short? ________
6. A heterozygous round seeded plant
(Rr) is crossed with a homozygous
round seeded plant (RR).
Complete a cross for two white
colored plants.
What % of their offspring will be white flowered?
What % of the offspring will be homozygous (RR)?
________
________
Name: _________________________________
9. A white flowered plant is crossed
with a plant that is heterozygous for
the trait.
What % of the offspring will have purple
flowers? ________
10. Two plants, both heterozygous
for the gene that controls flower
color are crossed.
What % of their offspring will have purple
flowers? ________
What % will have white flowers? ________
11. In guinea pigs, the allele for short
hair is dominant.
What genotype would a heterozygous short
haired guinea pig have? _______
What genotype would a homozygous short
haired guinea pig have? _______
What genotype would a long haired guinea
pig have? ________
Date: _________________
Period: ______
12. Show the cross for a pure
breeding short haired guinea pig
and a long haired guinea pig.
What % of the offspring will have short hair?
________
13. 14. Show the cross for two
heterozygous guinea pigs.
What % of the offspring will have short hair?
________
What % of the offspring will have long hair?
________
14.
CHALLENGE!
Two short haired guinea pigs are mated several times.
Out of 100 offspring, 25 of them have long hair. What
are the probable genotypes of the parents?
________ x ________
Show the cross to prove it!
Name: _________________________________
Date: _________________
Period: ______
CHALLENGE 1
Punnett Squares & GENDER
What are the chances that a specific genotype or phenotype will appear in a specific gender?
FIRST:
SECOND:
What are the chances of the trait
occurring?
What are the chances of the gender
occurring?
MOM
MOM
Genotype: ______
Genotype: ______
Phenotype: __________________
Phenotype: __________________
DAD
DAD
Genotype: ______
Genotype: ______
Phenotype: __________________
Phenotype: __________________
LAST:
What are the chances of the trait and the gender appearing together?
MULTIPLY…
X
=
(probability of trait occurring) X (probability of gender occurring)
=
=
%
(probability of BOTH occurring TOGETHER)
Name: _________________________________
Date: _________________
Period: ______
CHALLENGE 2
Punnett Squares & DIHYBRID CROSSES
What are the chances of two specific traits occurring together?
TRAIT 1: _____________
TRAIT 2: _____________
What are the chances of the trait occurring?
MOM
Genotype: ______
Phenotype: __________________
DAD
Genotype: ______
Phenotype: __________________
List the possible phenotypes seen in this Punnett Square below…
Name: _________________________________
Date: _________________
Period: ______
Challenge Practice Crosses! Show all work!
1. Brown eyes are dominant to blue eyes. A heterozygous mom is crossed with a homozygous dominant
dad. What percentage of the offspring will have brown eyes? ___________
What are the chances that they will have a brown eyed daughter? ___________
2. Curly hair is recessive and straight hair is dominant. A woman with curly hair marries a man who is
homozygous dominant for straight hair.
What percentage of the offspring will have curly hair? ___________
What are the chances they will have a curly haired son? ___________
3. Attached earlobes are dominant over free hanging earlobes. A mom who is homozygous dominant
marries a dad who is homozygous recessive.
What percentage of their offspring will have attached earlobes? ___________
What percentage of their offspring will have free hanging earlobes? ___________
What are the chances that they will have a daughter with free hanging earlobes? ___________
Name: _________________________________
Date: _________________
Period: ______
4. Please complete the following dihybrid cross for freckles and eye color. Freckles are dominant to no
freckles and brown eyes are dominant to blue eyes.
FF Bb X Ff Bb
What are the possible phenotypes of the children? List them below.
What are the chances of having a freckled blue-eyed child? _________________
What are the chances of having a non-freckled child? _________________
What are the chances of having a brown-eyed child? _________________
What are the chances of having a freckled brown-eyed child? _________________
Name: _________________________________
Date: _________________
Period: ______
5. Please complete the following dihybrid cross for tongue rolling and widow’s peak. Tongue rolling is
dominant to non-tongue rolling and widow’s peak is dominant to non-widow’s peak.
Tt Ww X Tt ww
What are the possible phenotypes of the children? List them below.
What are the chances of having a tongue rolling widow’s peaked child? _________________
What are the chances of having a non-widow’s peaked child? _________________
What are the chances of having a non-tongue rolling child? _________________
What are the chances of having a non-tongue rolling non-widow’s peaked child? ________________