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Complex Inheritance Punnett practice
1. In terriers (dogs) there are two coat types recognized by the American Kennel Club (AKC) as standard
for terrier breeds, smooth (straight-haired) and wire-haired (very tightly curled). Assuming coat type is
inherited by incomplete dominance, the coats can be smooth, wire-haired or wavy (this coat is not
accepted by the AKC). Do Punnett squares to answer the following.
a. When a smooth haired terrier is mated with a wire-haired one, what genotype(s) and phenotype(s)
result for coat type?
b. If a wire-haired terrier is mated with a wavy-haired terrier, what proportions of puppies would have
acceptable (by AKC standards) coats?
2. A palomino horse is golden in color (when viewed from a distance). Palomino color is very popular with
horse owners, but it is not a true breeding color. It results from mating a brown horse with a creamcolored horse. A close inspection of a palomino horse’s coat reveals alternating brown and creamcolored hairs. Choose letters for the traits, then do a Punnett square crossing two palomino horses and
predict how many of each horse color you can expect.
3.
Rabbit fur is controlled by a single gene with multiple alleles, as outlined in the table. Remember that
rabbits will have two alleles for coat color.
Phenotype
Allele
Pattern of inheritance
Dark gray coat (wild color)
C
dominant to all other alleles
Chinchilla
cch
dominant to Himalayan and white
Himalayan
ch
dominant to white
White
c
recessive
a) List all genotypes for the four different phenotypes—hint: there are 4, then 3, 2 and 1
combinations respectively.
b) A chinchilla rabbit is mated with a Himalayan, producing some white offspring (and others, too.)
What are the parent’s genotypes? Explain with a Punnett square.
4. Suppose height in a certain plant is controlled by two genes A and B. Plants are a minimum of 6” tall.
Each dominant gene the plant inherits adds 4” more in height. Each recessive gene adds nothing to the
plant height. Do a dihybrid cross of two 14” tall plants (AaBb X AaBb) and show the number of each
height plant you could expect (give the ratio out of 16 plants). Hint: the Punnett square will have 16
boxes in it. Use a separate sheet if you need more space.