Name: _________________________
Homework: Complex Patterns of Inheritance
Match the definition in Column A with the term in Column B.
Column A
Column B
______ 1.) a single gene that controls more than one trait.
A. co-dominance
______ 2.) occurs when the heterozygous phenotype is an
intermediate between the two homozygous
parent phenotypes
B. epistasis
______ 3.) a single trait that is affected by more than one
gene – a “dosage” effect
D. multiple alleles
C. incomplete dominance
E. pleiotropic gene
______ 4.) both alleles are expressed in the heterozygous
phenotype
F. polygenic trait
______ 5.) the interaction of two or more genes to control a
single phenotype
______ 6.) occurs when there are more than two alleles for
a single gene
Use your notes to answer the following questions completely. Use complete sentences where applicable.
Show all work and Punnett squares where applicable.
7.) In short horned cattle, alleles for red and white coats occur. A cross between a red (RR) bull and a
white (WW) cow produce offspring that appear reddish-gray or roan color.
 What type of inheritance is this? ________________________________
 A roan cow mates with a roan bull. What is the phenotype ratio of the offspring? ____________
8.) A man with blood type AB marries a woman heterozygous for blood type B.
 What type of inheritance is blood type in humans? ____________________________
 What are the genotypes of the parents? _______ x _______
 What is the chance that they could have a child with blood type A? _______
9.) The gene that causes sickle cell disease has two codominant alleles. A person with the genotype AA
has normal red blood cells. A person with the genotype SS has sickle-shaped red blood cells and
suffers from sickle cell disease. People with the heterozygous genotype, AS, have both normal and
sickle-shaped red blood cells, but do not suffer the same symptoms as people with sickle cell
disease.
 If two people heterozygous for sickle-cell disease marry and have children, what percentage of
their children will have sickle cell disease? __________
 People who are heterozygous for the sickle-shaped red blood cells also show resistance to the
disease malaria. What type of inheritance pattern is this? ____________________________
10.) Explain why the frequencies of the various human skin colors exhibits a bell curve pattern like the
one plotted in Figure 1 below. What type of inheritance pattern is this? _______________________
Figure 1
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11.) Propose a mechanism to explain why some pleiotropic genes are lethal when the homozygous
genotype is inherited.
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12.) Two separate unlinked genes effect mouse hair color. AA or Aa mice are agouti (natural coloration).
Mice with genotype aa are albino because all pigment production is blocked, regardless of the
phenotype of the second gene locus. At the second gene locus, the B allele (agouti coat) is dominant
to the b allele (black coat). What would be the result of a cross between two agouti mice of genotype
AaBb?
A. 4 agouti: 4 black: 8 albino
B. 9 agouti: 3 black: 3 albino: 1 grey
C. 9 agouti: 3 black: 4 albino
D. 8 agouti: 4 black: 4 albino
Note: This problem is most easily solved using a large 16-box Punnett square. For help with the
solution, consult the following internet link:
http://www.biology.arizona.edu/mendelian_genetics/problem_sets/dihybrid_cross/13t.html
12b.) What type of inheritance pattern is this? _____________________________________
Challenge Problem – Coat Color in Rabbits
5. A heterozygous chinchilla (gray) rabbit (c ch,ch) is bred with a heterozygous full color rabbit (Cc). What is
the chance that these parents could produce a himalayan rabbit?________ An albino rabbit? ________