phelanphys3e

7.9–7.15

7.9–How are genotypes translated into phenotypes?

The world in which each trait is coded for by a single gene with two alleles—one completely dominant and one recessive—and with no environmental effects at all doesn’t quite capture the complexity of the world beyond Mendel’s pea plants.

All of the offspring of a black hen and a white rooster are gray. The simplest explanation for this pattern of inheritance is:

a) multiple alleles.
b) codominance.
c) incomplete dominance.
d) incomplete heterozygosity.
e) sex linkage.

A woman with type B blood and a man with type A blood could have children with which of the following phenotypes?

a) AB only
b) AB or O only
c) A, B, or O only
d) A or B only
e) A, B, AB, or O

Which of the following traits shows a polygenic method of inheritance?

a) flower color in snapdragons
b) blood type in humans
c) seed color in peas
d) sickle-cell disease in humans
e) skin color in humans

The impact of a single gene on more than one characteristic is called:

a) incomplete dominance.
b) environmentalism.
c) balanced polymorphism.
d) pleiotropy.
e) codominance.

A rare, X-linked dominant condition in humans, congenital generalized hypertrichosis, is marked by excessive hair growth all over a person’s body. Which of the following statements about this condition is incorrect?

a) The son of a woman with this disease has just slightly more than a 50% chance of having this condition.
b) All daughters of a man with this condition will have the condition.
c) The daughter of a woman with this disease has just slightly more than a 50% chance of having this condition.
d) Every son of a woman with this disorder will have this condition.
e) The son of a man with this condition is no more likely to have the condition than the son of a man who doesn’t have the condition.

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