Essentials of Anatomy and Physiology

Human Development and Genetics 495

FOR FURTHER THOUGHT

1. Look at Table 21–1, and for each structure derived
   from each of the three primary germ layers, try to
   name a gene or set of genes that will be switched
   on. The gene or genes may be for a protein or a
   structure. Then try to name three genes that will
   be active in all of these different types of cells.


2. Women who smoke cigarettes should make spe-
   cial efforts to stop if they wish to have children, in
   part because nicotine causes vasoconstriction.
   Describe how maternal smoking would affect a
   fetus.


3. The use of fertility drugs may lead to multiple fer-
   tilizations and embryos. With six embryos, or even
   five, what problems will there be in the maternal
   uterus?


4. Sometimes during a pregnancy the placenta will
   become detached. Total detachment is a medical
   emergency. If detachment is only partial, even a lit-
   tle, there may still be problems for the fetus and the
   mother. Describe these.


5. Mr. and Mrs. Brown want to have children, but Mr.

Brown is hesitant. He had an older brother who

died of Duchenne’s muscular dystrophy, and he is

worried that he may have a gene that can be passed

on. “It’s recessive,” he tells you, “and doesn’t always

show up; it can skip a generation.” What can you

tell the Browns?

6. Mr. and Mrs. Gray have 6 children: 3 have type A
   blood and 3 have type B blood. Can we say with
   certainty what the two blood types of the parents
   are? Can we list possible pairs? Can we say with
   certainty what the parents’ blood types are not?
   (For example, Mr. and Mrs. Gray cannot both be
   type O.) Make a list of possible pairs, and a list of
   pairs that are not possible.


7. Your friends, the Kalliomaa family, are of Finnish
   descent, and they are having a family reunion.
   Another friend asks you how all of these people in
   three generations can have blond hair and blue
   eyes, because these are recessive traits, and dark
   hair and eyes are dominant. What can you tell your
   friend to explain this?


8. Describe the major pulmonary and circulatory
   changes that occur in the infant after birth.
   (p. 486)


9. What is the genetic material of chromosomes?
   Explain what a gene is. Explain why a person has
   two genes for each protein or trait. (p. 487)


10. Define homologous chromosomes, autosomes,
    and sex chromosomes. (p. 487)


11. Define allele, homozygous, heterozygous, geno-
    type, and phenotype. (p. 487)


12. Genetics Problem: Mom is heterozygous for

brown eyes, and Dad has blue eyes. What is the %

chance that a child will have blue eyes? Brown

eyes? (pp. 487–488)

14. Genetics Problem: Mom is homozygous for type
    A blood, and Dad is heterozygous for type B
    blood. What is the % chance that a child will
    have type AB blood? Type A? Type B? Type O?
    (p. 489)


15. Genetics Problem: Mom is red-green color blind,
    and Dad has normal color vision. What is the %
    chance that a son will be color blind? That a
    daughter will be color blind? That a daughter will
    be a carrier? (pp. 490–491)