C h a p t e r 6
Genetic and Congenital Disorders
127
R E V I EW E X E R C I S E S
1.
A 23-year-old woman with sickle cell disease and
her husband want to have a child, but worry that
the child will be born with the disease.
A.
What is the mother’s genotype in terms of
the sickle cell gene? Is she heterozygous or
homozygous?
B.
If the husband is found not to have the sickle
cell gene, what is the probability of their child
having the disease or being a carrier of the sickle
cell trait?
2.
A couple has a child who was born with a
congenital heart disease.
A.
Would you consider the defect to be the result of
a single-gene or a polygenic trait?
B.
Would these parents be at greater risk of having
another child with a heart defect, or would they
be at equal risk of having a child with a defect
in another organ system, such as cleft palate?
3.
A couple has been informed that their newborn
child has the features of Down syndrome. It was
suggested that genetic studies be performed.
A.
The child is found to have trisomy 21. Use
Figure 6-8 to describe the events that occur
during meiosis to explain the origin of the third
chromosome.
B.
If the child had been found to have the
robertsonian chromosome, how would you
explain the origin of the abnormal chromosome?
4.
A 26-year-old woman is planning to become
pregnant.
A.
What information would you give her regarding
the effects of medications and drugs on the
fetus? What stage of fetal development is
associated with the greatest risk?
B.
What is the rationale for ensuring that she
has an adequate intake of folic acid before
conception?
C.
She and her husband have an indoor cat. What
precautions should she use in caring for the cat?
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