Genetics - X Linked Genes
**In fruit flies, eye color is a sex linked trait. Red is dominant to white.**
1. What are the sexes and eye colors of flies with the following genotypes?
X R X r _________ X R Y __________ X r X r __________
X R X R ____________ X r Y ____________
2. What are the genotypes of these flies:
white eyed, male ____________ red eyed female (heterozygous) ________
white eyed, female ___________ red eyed, male ___________
3. Show the cross of a white eyed female X r X r with a red-eyed male X R Y .
4. Show a cross between a pure red eyed female and a white eyed male.
What are the genotypes of the parents:
___________ and _______________
How many are:
white eyed, male ____
white eyed, female ____
red eyed, male ____
red eyed, female ____
5. Show the cross of a red eyed female (heterozygous) and a red eyed male.
What are the genotypes of the parents?
___________ & ________________
How many are:
white eyed, male ____
white eyed, female ____
red eyed, male ____
red eyed, female ____
Math: What if in the above cross, 100 males were produced and 200 females. How many
total red-eyed flies would there be? ________
OOMPA LOOMPA GENETICS
Show your work!
Key:
________ = Gray face
________ = Gray face
________ = Orange face
Monohybrid Crosses
1. OOmpas generally have gray faces, which is caused by a dominant gene. The
recessive condition results in an orange face. Develop a key to show the possible
genotypes and phenotypes for the OOmpah's face colors.
2. Two heterozygous OOmpahs are crossed. What proportion of the offspring will have
orange faces? ________
3. A gray faced OOmpah (homozygous) is married to an orange faced Oompah. They
have 8 Oompah children. How many of those children will have gray faces? _______
4. Otis Oompah has an orange face is is married to Ona OOmpah who has a gray face.
They have 60 Oompah children, 30 of those children have orange faces. What is Ona and
Otis OOmpah's genotype? _______________Show the cross.
5. Odie Oompah has a gray face, in fact everyone in Odie’s family has a gray face, and
the family likes to brag that they are a “pure” line. Much to his familys horror, he married
Ondi Oomah, who *gasp* has an orange face. What will be the phenotypes of their
children? ________ What are the genotypes of the children? __________
6. Ona Oompah (from #4) divorces Otis and marries Otto. Otto has a gray face, but is
heterozygous. What is the probability that Ona and Otto's children will have an orange
face?
Incomplete Dominance
______ = Red Hair
______ = Purple Hair
______ = Blue Hair
7. OOmpahs can have red, blue, or purple hair. The allele that controls this trait is
INCOMPLETELY DOMINANT, where purple hair is caused by the heterozygous condition.
Show a "key" for the genotypes and phenotypes of hair color.
8. Orville Oompah has purple hair and is married to Opal Oompah who brags that she has
the bluest blue hair in the valley. How many of Opal children will be able to brag about
their blue hair also. _____ How many will take after their father? ____
9. One of Opal's children is born with shocking red hair. Is Orville Oompah the father of
this child? ______But wait, Opal swears that she has been faithful, she claims the hospital
goofed and got her baby mixed with someone else's. Is Opal the mother of the red haired
child?
10. Olga Oompah has red hair and marries Oliver Oompah who has blue hair. They have
32 children. What is the color of these children's hair? ____________
11. Olivia Oompah is married to Odo Oompah. Both of them have purple hair. They have
100 children. What is the hair color of their children and in what proportion?
Red ________ Blue ______ Purple ________
12. In the land of OOmpah, blue hair is highly valued. Blue haired OOmpahs get special
benefits. Oscar Oompah has purple hair but he wants a wife that will give him children
with blue hair.
What color hair should he look for in a wife? __________
If he can’t find this type of Oompah what should be his second choice? _____________
13. Ophelia Oompah is not married but she wants to have children. She goes to a fertility
clinic where she is fertilized by an anonymous sperm donor. Ophelia has red hair. 5
months later, a litter of oompahs is born, of the eight babies in the litter, 4 of them have
red hair, and 4 of them have purple hair. What color hair did the babies’ father have?
____________ (Show the cross)
14. Ophelia repeats the process a year later. This time she has a litter of 5 oompahs, all of
which have purple hair. What was the father’s hair color in this case? ___________
(Show the cross)
Dihybrid Cross
15. A homozygous gray faced, blue haired oompah named Ortimer marries an orange
faced (homozygous) red haired oompah named Odette. GGBB x ggRR What will Ortimer
and Odette’s children look like? ______________________
16. Two oompahs, both heterozygous for both traits are married. Out of 16 children, how
many of each type would you expect?
Human Sex Linkage
6. In humans, hemophilia is a sex linked trait. Females can be normal, carriers, or have
the disease. Males will either have the disease or not (but they won’t ever be carriers)
X H X H = female, normal
X H X h = female, carrier
X h X h = female, hemophiliac
X H Y = male, normal
X h Y= male, hemophiliac
Show the cross of a man who has hemophilia with a woman who is a carrier.
What is the probability that their children will have the disease? __________
7. A woman who is a carrier marries a normal man. Show the cross. What is the
probability that their children will have hemophilia? What sex will a child in the family with
hemophilia be?
8. A woman who has hemophilia marries a normal man. How many of their children will
have hemophilia, and what is their sex?
Calico Cat Genetics
9. In cats, the gene for calico (multicolored) cats is codominant. Females that receive
a B and an R gene have black and oRange splotches on white coats. Males can only be
black or orange, but never calico.
Here’s what a calico female’s genotype would look like: X B X R
Show the cross of a female calico cat with a black male?
What percentage of the kittens will be black and male? _________
What percentage of the kittens will be calico and male? _________
What percentage of the kittens will be calico and female? _________
10. Show the cross of a female black cat, with a male orange cat.
What percentage of the kittens will be calico and female? _____What color will all the
male cats be? ______