Name ____________________________________
Incomplete, Codominance, Polygenic, and Multiple Alleles
A. Tail length in cats is an incomplete dominant trait. A gene for a long tail and a gene for no tail produce a cat
with a short tail. A cat with no tail is crossed with a cat with a long tail.
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What is the genotype of a cat with no tail? __________
What is the genotype for a cat with a short tail? ___________
What is the genotype for a cat with a long tail? _____________
What genotype(s) are produced in the offspring? ______________________
What phenotype(s) are produced in the offspring? _____________________
What is the probability of producing a cat with a long tail? _____________
What is the probability of producing a cat with a short tail? ____________
Draw the Punnett Square on the right.
B. Cow color is a codominant trait. Red and white genes form a roan color. (Both red and white hairs in the coat)
A roan bull is crossed with a roan cow.
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Diagram a Punnett Square for the cross.
What is the genotype of the parents? _________________________
What are the possible genotypes of the offspring? _______________
What are the possible phenotypes of the offspring? ______________
What is the genotypic ratio? ________________________
What is the phenotypic ratio? _______________________
C. Chicken color is a codominant trait. Black Andulasian chickens and white Andulasian chickens form “blue”
chickens. (A combination s black and white feathers on the same bird.) A white rooster is crossed with a “blue”
chicken.
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Diagram a Punnett Square for this cross.
Will any offspring be white? _____________
Will any of the offspring be black? _______________
Will any of the offspring be blue? ______________
What is the genotypic ratio? _________________
What is the phenotypic ratio? ____________________
D. Blood type is a codominant trait. A man with blood type A marries a woman with blood type B
Half the children have blood type AB and half have blood type A.
27. Diagram the Punnett square for this couple.
28. What is the genotype of the father? ______________________
29. What is the genotype of the mother? _____________________
30. What is the genotype of the children with blood type A? _____________
31. What is the genotypic ratio? ________________________
32. What is the phenotypic ratio? _______________________
33. What is the probability of producing a child with blood type A? ____________
34. What is the probability of producing a child with blood type B? ____________
35. What is the probability of producing a child with blood type O? ____________
E. A man with blood type AB marries a woman with unknown blood type. The children all have either blood type A or B.
36. What is the genotype for the mother that will produce only children
with A or B blood type?__________________
37. What is the mother’s phenotype? ____________________
38. What is the genotype for the children with blood type A? ______________
39. What is the genotype for the children with blood type B? ______________
40. What is the genotypic ratio? ______________________
41. Diagram a Punnett square for this couple.
F. In a certain cactus, prickly spines can be two pronged or one pronged. If a true breeding one-pronged cactus is crossed
with a true breeding two-pronged cactus, the F1 generation has a mixture of spines, some are two-pronged, and some
are one-pronged.
42. Is this an example of codominance or incomplete dominance?
43. Show the F2 generation (a cross between the two F1's).
44.What are the phenotypes of the offspring and in what proportion (ratio)?
In this same cactus, if you cross a plant that has red flowers to one that has yellow flowers, you produce a plant that has
orange flowers.
45. Is this codominance or incomplete dominance?
46. Show the cross of an orange flowered plant to a red flowered plant.
47. What is the probability of producing a yellow flower?
A red flowered, two-pronged cactus is crossed with a yellow flowered one-pronged
cactus.
48. What are the parents’ genotypes? _____________________________________
49. What is the probability of producing a red, two-pronged cactus? __________
50. What is the probability of producing a yellow, one-pronged cactus? __________
51. What is the probability of producing an orange, one- pronged cactus? ___________
52. What is the probability of producing an orange, one and two pronged cactus? ________
Show the cross of a cactus that is heterozygous for both traits crossed with one that has red flowers and one-pronged
spikes.
53. What is the genotypic ratio? ___________________
54. What is the phenotypic ratio? ____________________
G. Dwarfism in humans is a dominant trait that is also lethal if an individual inherits two copies. Show the genotypes of a
family where both parents are dwarfs and they have 2 children, where one is a
dwarf and the other is not.
H. Guinea pigs can have curly or straight hair, where the curly gene is recessive. Guinea pigs can also have a condition
called bowlegged, where their legs curve noticeably outward. Bowleggedness is a dominant lethal allele if an individual
inherits two copies of it (BB). Show the cross between a curly haired, bowlegged guinea pig and a heterozygous straight
haired pig that is also bowlegged.
55. What fraction of their offspring would you expect to be normal with curly hair?
What fraction would you expect to die?
What is the phenotypic ratio of the living progeny?
I. In Snarlymonsters, the number of teeth is polygenic. The recessive condition (aabbcc) results in a
toothless Snarlymonster, and the dominant condition (AABBCC) results in a Snarlymonster with 6
teeth. There are 5 other possible variations.
56. How many teeth would an AaBbCc Snarlymonster have? ______
57. List the phenotypic ratios (how many teeth) of all the potential offspring for the cross
AABBCc x AAbbcc .
J. Lethal white overo syndrome is an autosomal recessive gene which is fatal 100% of the time
and occurs in horses. Death of OLWS foals occurs within a few days of birth. If heterozygous, the
animal has a multicolored patterned appearance, sometimes called a "paint". This pattern
indicates the horse is heterozygous. If two of these paint horses were bred, what percentage of
their offspring would survive and what percentage would die from OLWS?
K. Skin color in humans is determined by a polygenic inheritance system, possibly involving as many as 9 genes. For
simplicity, let’s consider the influence of 3 genes: A, B, and C where the dominant allele darkens skin color. Suppose a
women with genotype AABbCc has offspring with a male who has genotype AaBbcc.
58. List all the possible genotypes of the gametes that could be produced by each parent.
59. The darkest offspring possible for this cross would have how many dominant genes?
60. The lightest offspring possible for this cross would have how many dominant genes?
L. Multiple Alleles for Rabbit Fur Color
Examine the information above for multiple alleles in rabbit fur color.
61. What are the possible genotypes that would produce a wild-type phenotype?
62. Diagram a Punnett Square for a rabbit that is a Chinchilla-Himalayan
hybrid and an albino rabbit.
63. What is the phenotype for the Chinchilla-Himalayan hybrid above?
_________________________________
64. What is the probability of producing a wild-type offspring? __________
65. What is the probability of producing a Himalayan offspring? ___________
66. What is the probability of producing a chinchilla offspring? ____________
67. What is the probability of producing an albino offspring? _____________
68. What is the phenotypic ratio? _______________________________