Usually, I do simpler worksheets first, the word problems on this page can prove overly daunting for beginners. The "keys" are designed to help them make sense of the problem. It is not unusual for students to look at this sheet and just decide they'll take the zero because it just looks too hard. In my class, this isn't an option, and I'll sit next to them, walk them through it and basically annoy them until they decide they will at least try it.

You will always have those students who move quickly through the problems. If they have the right personality, you can ask them to move around the class and help others who may be stuck.

Also, the original worksheet had blue and orange faces, but this got confusing with the letters for the blue/red/purple hair, so I changed the face color to gray to make the letters different.

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.

GG___ = Gray face
Gg____ = Gray face
_gg__ = Orange face

2. Two heterozygous OOmpahs are crossed. What proportion of the offspring will have orange faces? ________


1/4 , 25% 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? _______ GG x gg = Gg, all 8 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. 

Gg x ggpunnett

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? __all will have gray faces____ What are the genotypes of the children? ___Gg_____

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?  ___ Gg x Gg = 25% orange faced children

Incomplete Dominance

__RR___ = Red Hair
__BR__ = Purple Hair
__BB__ = 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? ____ BR x BB, 1/2


9. One of Opal's children is born with shocking red hair. Is Orville Oompah the father of this child? __no__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? she can't be the mother either, there's no way opal who is BB (blue) can have any children with red hair.

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?

BB x RR = all BR, purple

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 __25%_____ Blue _25%___ Purple __50%___


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? ____blue would be best, would give him 50% blue haired offspring____
If he can’t find this type of Oompah what should be his second choice? __purple would give him 25%________

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)

RR x BR would give you about 50/50 red to blue haired offspring

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? _father must have been blue haired__RR x BB__
(Show the 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? ______________________

You can do this a couple of different ways, if students have not had experience with dihybrids you can tell them to separate the traits, and figure out what color faces they have GG x gg and what color hair they will have BB x RR. Without even doing a square, you can easily find out what the children look like, all will be Gg (grey) with BR (purple) hair.

16. Two oompahs, both heterozygous for both traits are married. Out of 16 children, how many of each type would you expect? This cross is quite involved, GgBR x GgBR, you'll need to set up a square that looks like this:

3/16 gray face, blue hair
6/16 gray face, purple hair
3/16 gray face, red hair

1/16 orange face, blue hair
1/16 orange face, red hair
2/16 orange face, purple hair