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Genetics Practice Problems (single trait crosses)
Courtesy of The Biology Binder (questions 1-7)
Pictured above is an alien who displays all of the dominant characteristics of its species. Below is a chart listing
various traits found in this alien race. Use the information in the chart to solve the genetics problems that follow.
Trait
Body color
Number of Antennae
Eye color
Eyesight
Number of Body Rings
Dominant Phenotype
(Y)
(A)
(P)
(E)
(R)
Yellow
2
Purple
Glasses needed
3
Recessive Phenotype
(y)
(a)
(p)
(e)
(r)
Orange
1
White
Glasses not worn
5
1. A heterozygous male mates with a pure yellow female. What is the chance this couple will produce an orange baby? Check your
answer
2. Two purple-eyed aliens mate. Both aliens are hybrid for the eye color trait. What is the chance this couple will produce a baby with
a homozygous recessive genotype? Check your answer
3. A heterozygous female with 3 body rings mates with a 5-ringed male. What is the chance that this couple will have a baby that looks
like its mother? Check your answer
4. A pure male alien displaying the dominant body color mates with a female that is homozygous recessive for this characteristic.
What is the chance that this couple will have a baby with a hybrid genotype? Check your answer
5. A male alien with 1 antenna mates with a female alien who has 2 antennae. The female is heterozygous for the antenna trait. What
is the chance that this couple will produce a baby with the recessive phenotype? Check your answer
6. An alien couple, both of which wear glasses, are having a baby. The male's genotype is heterozygous. The female is
phenotypically dominant but does carry the recessive allele. What is the chance that this couple's baby will have to wear glasses?
Check your answer
7. A 3-ringed female mates with a homozygous male. The female has been genetically tested and is carrying both the dominant and
the recessive allele for this trait. The male displays the recessive phenotype. What is the chance that this couple will have a
genetically pure baby? Check your answer
In humans, "unattached" earlobes are dominant over "attached" earlobes. "Widows peak" hairline is dominant
over "non-widows peak" hairline. Use E and e for the earlobe phenotype alleles, and W and w for the hairline
phenotype alleles.
8. A female and a male, both with unattached earlobes, have a child with attached earlobes. What is the probability their
next child will have attached earlobes?
9. A female and a male, both with genotype Ee have a child. What is the probability it will have attached earlobes?
10 A female and a male, both with genotype EE. What is the probability it will have attached earlobes
11. A female with a widows peak hairline and a male with no widows peak hairline have a child. What are the chances of
having a child with no widows peak hairline.
12. A nurse at a hospital removed the wrist tags of three babies in the maternity ward. She needs to figure out
which baby belongs to which parents, so she checks their blood types. Using the chart below, match the baby to
its’ correct parents. Show the crosses to prove your answers.
Parents
Mr. Apple
Mrs. Apple
Mr. Plum
Mrs. Plum
Mr. Orange
Mrs. Orange
Blood Types
O
A
AB
AB
O
O
Baby
Jackie
Ryan
Holly
Blood Type
O
A
B
13. A child has A blood. What are ALL the possible blood types of his parents? Show each cross to prove
that it is possible.
14. If a child has B blood and mom is O blood and dad is AB blood. Is it possible that he is the father?
Show your work to prove your answer.
15. If Sue is AB blood type and Louie is homozygous A blood, what are the possible genotypes and
phenotypes?
16. If Joe is heterozygous B blood and Julie is homozygous A blood, what are the chances of having a child
with AB blood?