Name: __________________________________
Date: ________________
Unit 5C Genetic Inheritance
Study Guide
1. What is the rule of dominance? Who developed this idea?
Some alleles are dominant over others. If both the dominant and recessive alleles are present, the dominant will be
expressed. Gregor Mendel
2. Which of the following is homozygous dominant, heterozygous, and homozygous recessive (label)?
Tt
TT
tt
Heterozygous
Homozygous dominant
Homozygous recessive
3. Complete a punnett square for two parents that are heterozygous tall.
T
T
t
TT
Tt
Tt
t
tt
4. In the punnett square you created, the letters you placed across the top and down the sides represent…
____The alleles in each gamete combination from the parent______________
5. The letters inside the boxes represent…
______The potential genotypes of the offspring created by fertilization _______________________
6. If the plants in the cross above create 100 offspring, how many of them will be tall? _____75________
7. In a monohybrid cross, what is the genotype ratio of offspring when both parents are heterozygous? __1:2:1___
8. In a monohybrid cross, what is the phenotype ratio of offspring when both parents are heterozygous? __3:1___
9. What is a test cross and how is it done?
_____A way to determine of an organism with the dominant phenotype is homozygous dominant or heterozygous.
Cross the organism in question with a homozygous recessive organism and look at the offspring. _____________
10. Set up a dihybrid cross for a female dog who is BBEe and a male dog who is bbEE. (B for barking and E for erect
ears). BE
Be
BE
Be
(Did you FOIL the parents?!)
bE
bE
BbEE
BbEe
BbEE
BbEe
BbEE
BbEe
BbEE
BbEe
BbEE
BbEe
BbEE
BbEe
BbEE
BbEe
BbEE
BbEe
bE
bE
11. How many offspring (out of 16) in the cross above will be heterozygous for both traits? __8/16 or
1/2____________
12. How many offspring (out of 16) in the cross above will be barking and have erect ears? __16/16 or
100%___________
13. In a dihybrid cross, if both parents are heterozygous for both genes, what will the phenotypic ratio be for the
offspring? ___9:3:3:1______
14. What is the difference between incomplete dominance and codominance (give an example of each).
_____Incomplete dominance produces a blending effect due to neither allele being fully dominant (pink flowers
from red and white parents). Codominance expresses both alleles (speckled chickens have both black and white
feathers). _______
15. What is the difference between multiples alleles and polygenic traits? ________Multiple alleles refers to more
than two possible alleles for ONE gene (each person will only inherit 2 however). Polygenic traits are traits
control by more than one GENE. __________________
16. Do you know the possible genotypes for each blood type? You should!
17. Set up a punnett square for a homozygous type A mom and a type AB dad.
IA
IA
IA
IB
IA IA
IA IA
IA IB
IA IB
What percent of offspring will be type AB? ____50%________
What percent of offspring will be type O? ____0%_______
18. What is sex linked inheritance? _______Some traits are inherited from genes on the X and Y chromosome. Since
males and females have different sex chromosome, these genes will be inherited differently. Genes on the Y
chromosome are passed father to son. _______________
19. Why are disorders caused from defective genes on the X chromosome more common in males? ______Males
only have one X chromosome so if a gene on that X is defective they will have the disorder. Females have a
second X and a back-up . ______________________________________________
20. Review the colorblindness example from the notes packet.
21. Review your One Trait Crosses Review Packet.
22. What is a pedigree? Know what the symbols and shadings mean.
_________ chart that shows patterns of inheritance in a family. _________________________________
23. Review how to determine the genotypes of individuals using a pedigree.
24. Use the pedigree below to answer the following questions:
 Why are some shapes shaded in? _________shaded shapes represent individuals with the trait in
question. ____________________________________________________________________________

In this pedigree, the trait in question is a dominant trait (P). Based on this information, what is the
genotype of individual #3? Explain. ____pp because it is not shaded and thus does not have the trait.
Since the trait is dominant, to not have the trait the genotype must be homozygous recessive. _______
_____________________________________________________________________________________

What is the genotype of individual #1? Explain. __Pp (heterozygous) because this individual has a child
that is pp, so he must have a “p” in his genotype to pass down to the child. _______