Download Name

Name: ___________________________________________________
Period: ______ Date: _________
Punnett Squares Worksheet #3
1. In snapdragons, no color is dominant. Plants with two copies of one allele (RR) have red
flowers, while plants with the other allele (WW) have white flowers. An intermediate (in
between) phenotype occurs in heterozygous plants (RW): pink flowers!
a. What is the name for this mode of inheritance?
b. Cross a red snapdragon with a white snapdragon.
What will the genotype be for the offspring? ________
What will the phenotype be for the offspring? ________
RR = red
WW = white
RW = pink
c. Cross a pink snapdragon with another pink snapdragon.
What is the genotype ratio?
________________________________________
What is the phenotype ratio?
________________________________________
d. Two snapdragons were crossed and produced 1000 seeds. When they were
planted, 498 of them had red flowers; 502 of them had pink flowers. What were
the likely genotypes of the parent plants? Hint: work backwards!
2. Human blood types are determined by a single gene with three different alleles: A, B
and O. Both the A and B alleles are dominant to O. A and B are codominant to each
other. See the table below:
Genotype
Phenotype
AA
A
AO
A
BB
B
BO
B
AB
AB
OO
O
a. A man with type AB blood marries a woman with type O blood.
What are the possible genotypes for their offspring?
_____________________________________________
b. Could a mother with type B blood and a father with type O blood produce
offspring with type O blood? Hint: set up the two possible Punnett squares to
solve this problem, given that more than one genotype can give the same
phenotype.
What must the mother’s genotype be in order to have a child with type O blood
(with this particular father)?
__________________________
Is she homozygous or heterozygous for this trait if she has a child with type O
blood?