132 ■ CHAPTER 07 Patterns of Inheritance
THE QUESTIONS
The Basics
(^1) Link each term with the correct definition.
GENOTYPE 1. An individual that carries one copy each of two
different alleles (for example, an Aa individual or
an IB individual).
PHENOTYPE 2. An individual that carries two copies of the same
allele (for example, an AA, aa, or II individual).
HETEROZYGOTE 3. An allele that does not affect the phenotype
when paired with a dominant allele in a
heterozygote.
HOMOZYGOTE 4. The genetic makeup of an individual; more
specifically, the two alleles of a given gene that
affect a specific genetic trait in a given individual.
DOMINANT 5. The specific version of a genetic trait that is
displayed by a given individual.
RECESSIVE 6. The allele that controls the phenotype when
paired with a different allele in a heterozygote
individual.
(^2) Select the correct terms:
The (gene / allele) for coat color has two (genes / alleles)—one for
brown coloring and one for black.
(^3) Select the correct terms:
Cells undergo (mitosis / meiosis) to become gametes. This process
sorts the alleles of a gene into separate gametes, which is the
basis for Mendel’s law of (segregation / independent assortment).
Genes on different chromosomes also sort into separate gametes
during this process, which is the basis for Mendel’s law of
(segregation / independent assortment).
(^4) For each of the following cases, identify whether the described
trait is an example of Mendelian inheritance (M) or a more complex
form of inheritance (C).
a. brown versus black coat color in dogs
b. body size in dogs
c. coat color in Siamese cats
d. skin color in humans
e. flower color in pea plants
allele is able to exert its full
effect. When the effect of
the two alleles is equally
visible in the phenotype of
the heterozygote, the pair of
alleles shows codominance.
● (^) Complex traits have patterns
of inheritance that Mendel’s
laws cannot predict. In
pleiotropy, for example,
a single gene influences
a number of different
traits. Polygenic traits, by
contrast, are governed by
the action of more than one
gene. And in epistasis, the
phenotypic effect of the
alleles of one gene depends
on the presence of alleles
for another, independently
inherited gene.
(^5) A single phenotype that results from a combination of two
different genes in which one gene interferes with the expression of
another gene is known as
(a) pleiotropy.
(b) complete dominance.
(c) incomplete dominance.
(d) codominance.
(e) epistasis.
(^6) Before Mendel conducted his experiments with pea plants,
people believed that offspring were a “blend” of their parents
and would show intermediate levels of their parents’ traits.
What would Mendel’s F 1 pea flowers have looked like if this
were true?
(a) white
(b) purple
(c) red
(d) yellow
(e) light purple
Challenge Yourself
(^7) A riddle: In my type of inheritance, the F
1 offspring of a true-
breeding black parent and a true-breeding white parent are all
gray. What type of inheritance am I?
(^8) Some time ago, you noticed that the sunflowers in your garden
were either tall or short—nothing in between. You bred the tall
sunflowers for many generations, until you felt confident that they
“bred true,” and you did the same for the short sunflowers. You
then set up a parental cross (P), and all of the resulting F 1 offspring
were short sunflowers. From this experiment, you conclude that
the short phenotype is
(a) pleiotropic.
(b) recessive.
(c) true-breeding in the F 1 generation.
(d) dominant.
(e) incompletely dominant.
(^9) In chickens, a mutant gene called frizzle causes not only
feathers that curl outward like a Labradoodle’s fur, but also an
abnormal body temperature, an increased metabolism, and fewer
eggs laid than by a normal chicken. From this information, you can
conclude that the frizzle gene is.