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Concept Check Questions
14.3
A rooster with gray feathers is mated with a
hen of the same phenotype. Among their
offspring, 15 chicks are gray, 6 are black,
and 8 are white. What is the simplest
explanation for the inheritance of these
colors in chickens? What phenotypes
would you expect in the offspring resulting
from a cross between a gray rooster and a
black hen?
Concept Check Questions
14.3
In humans, tall parents tend to have tall
children, and short parents tend to have
short children. Adult heights, however,
vary in the population over a wide
range, following a normal bell-shaped
curve. Explain these observations.
Concept Check Questions
14.4
Beth and Tom each have a sibling with
cystic fibrosis, but neither Beth nor Tom
nor any of their parents have the
disease. Calculate the probability that
if this couple has a child, the child will
have cystic fibrosis. What would be the
probability if a test revealed that Tom is
a carrier but Beth is not?
Concept Check Questions
14.4
Joan was born with six toes on each
foot, a dominant trait called polydactyly.
Two of her five siblings and her mother,
but not her father, also have extra
digits. What is Joan’s genotype for the
number-of-digits character? Explain
your answer. Use D and d to symbolize
the alleles for this character.
Concept Check Questions
15.1
Which of Mendel’s laws relates to the
inheritance of alleles for a single
character? Which law relates to the
inheritance of alleles for two characters
in a dihybrid cross? What is the
physical basis of these laws?
Concept Check Questions
15.2
When two genes are located on the
same chromosome, what is the
physical basis for the production of
recombinant offspring in a test cross
between a dihybrid parent and a
double-mutant parent?
Concept Check Questions
15.2
Genes A, B, and C are located on the
same chromosome. Test crosses show
that the recombinant frequency
between A and B is 28% and between A
and C is 12%. Can you determine the
linear order of these genes?
Concept Check Questions
15.3
Neither Tim nor Rhoda has Duchenne
muscular dystrophy, but their firstborn
son does have it. What is the
probability that a second child of this
couple will have the disease?
Concept Check Questions
15.4
More common than completely
polyploid animals are mosaic
polyploids, animals that are diploid
except for patches of polyploid cells.
How might a mosaic tetraploid—an
animal with some cells containing four
sets of chromosomes—arise?
Concept Check Questions
15.4
About 5% of individuals with Down
syndrome have a chromosomal
translocation in which one copy of
chromosome 21 is attached to
chromosome 14. How could this
translocation in a parent’s gonad lead
to Down syndrome in a child?
Concept Check Questions
15.4
Explain how a male cat could have the
tortoise shell phenotype.
Concept Check Questions
15.5
Gene dosage, the number of active
copies of a gene, is important to proper
development. Identify and describe two
processes that help establish the
proper dosage of certain genes.
Concept Check Questions
15.5
Reciprocal crosses between two primrose
varieties, A and B, produce the following
results:
A female x B male → offspring with all green
(nonvariegated) leaves.
B female x A male → offspring with spotted
(variegated) leaves.
Explain these results.
Concept Check Questions
15.5
Mitochondrial genes are critical to
the energy metabolism of cells, but
mitochondrial disorders caused by
mutations in these genes are
usually not lethal. Why not?