A Deadly Inheritance ■ 151Challenge Yourself
(^5) Sickle-cell disease is inherited as a recessive genetic disorder in
humans; the normal hemoglobin allele (H) is dominant to the sickle-
cell allele (h). For two parents of genotype Hh (carriers), construct a
Punnett square to show the possible genotypes of their children.
(^6) Which of the following correctly predicts the possible
genotypes of the children from question 5?
(a) 1 /^4 HH,^1 /^4 Hh,^1 /^2 hh
(b) 1 /^2 HH,^1 /^2 Hh
(c) 1 /^2 HH,^1 /^2 hh
(d) 1 /^4 HH,^1 /^2 Hh,^1 /^4 hh
(e) 1 /^4 HH,^3 /^4 Hh
(^7) Which of the following correctly predicts the possible
phenotypes of the children from question 5?
(a) 1 /^4 normal,^3 /^4 sickle-cell disease
(b) all normal
(c) all sickle-cell disease
(d) 1 /^2 normal,^1 /^2 sickle-cell disease
(e) 3 /^4 normal,^1 /^4 sickle-cell disease
(^8) Given that the normal hemoglobin allele (H) is dominant to
the sickle-cell allele (h), each time two Hh individuals have a child
together, what is the chance that the child will have sickle-cell
disease?
(a) 0%
(b) 75%
(c) 25%
(d) 50%
(e) 100%
(^9) Which of the following karyotypic sex chromosome
abnormalities result(s) in a male phenotype? (Select all that apply.)
(a) XO
(b) XXY
(c) XXX
(d) XYY
(e) XXXY
(f) XY with a complete deletion of the SRY gene
Tr y Something New
(^10) On the Indonesian island of Bali, about (^3) / (^4) of the feral (stray)
cats have a stumpy tail, while only^1 /^4 of the cats have a long tail.
Experiments in which a bunch of random stumpy-tailed cats were
mated with each other yielded some stumpy-tailed kittens and
some long-tailed kittens. The same experiments with long-tailed
(c) They are almost normal but show an intermediate phenotype
for the trait.
(d) They are completely normal and do not physically show the
trait.
(^3) Match each of the following terms with the correct definition.
GENE THERAPY
- A procedure in which cells
are gently suctioned from a
pregnant woman’s uterus to
test for genetic disorders in
the fetus.
IN VITRO
FERTILIZATION- A procedure in which a small
amount of fluid (and fetal
cells within it) is carefully
extracted from a pregnant
woman’s uterus to test for
genetic disorders in the
fetus.
PREIMPLANTATION GENETIC
DIAGNOSIS (PGD)- A treatment approach
that seeks to correct a
genetic disorder by insert-
ing healthy copies of the
mutated genes responsible
for the disorder.
CHORIONIC VILLUS SAMPLING
(CVS)- A procedure in which one
or two cells are removed
from a developing embryo
and tested for genetic
disorders; embryos that are
free of genetic disorders
may then be implanted into
a woman’s uterus.
AMNIOCENTESIS- A procedure in which
an egg is fertilized in a
petri dish, after which
one or more embryos are
implanted into a woman’s
uterus.
(^4) In the karyotype shown here, identify the sex chromosomes. Is
this individual a male or a female?