Chapter 23 - Human Genetic Traits

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Terms to Know in This Chapter:

identical twins

fraternal twins [frah TUR nul]

color blindness

hemophilia [he moe FILL ee ah]

cri-du-chat [cree due sha]

Down's syndrome

Patau syndrome [pa TAOW]

Edward's syndrome

Turner's syndrome

Klinefelter's syndrome

Trisomy X [TRY so me]

What You Need to Know:

You should be able to:

1. explain the following human genetic traits and state which condition is dominant and which is recessive:
   a. eye color,
   b. hair pattern (cowlicks),
   c. hair pattern number,
   d. PTC paper,
   e. red blood cells,
   f. middle finger hair,
   g. finger length (male),
   h. finger length (female),
   i. pattern baldness,
   j. finger nail shape,
   k. color blindness,
   l. hemophilia,
   m. widow's peak,
   n. earlobes,
   o. bent little finger,
   p. dimples,
   q. hitchhiker's thumb,
   r. big toe length,
2. identify the following syndromes, the causes, and be familiar with the phenotypic characteristics:
   a. cri-du-chat,
   b. Down's,
   c. Patau,
   d. Edward's,
   e. Turner's,
   f. Klinefelter's,
   g. Triple X,
3. state some common genetic facts and fallacies, and be able to separate fact from fiction, and,
4. be able to construct a pedigree chart from information in a family history.

Exercises: Fill in the Blank.

1. Most red blood cells are in shape; therefore, they are dominant. (round, oval)
2. Hemophilia is a recessive characteristic; therefore, more males than female will exhibit the trait. (sex-linked, sex-limited, sex-influenced)
3. Hitchhiker's thumb relates to the dominant trait of .
4. In males, the genotypes and would indicate someone with male pattern baldness.
5. In females, the forefinger is (longer, shorter) than the ring finger as a dominant trait.
6. The absence of a widow's peak is a trait. (dominant, recessive)
7. The detection of the short arm of chromosome #5 results in a condition known as which has the unusual feature of the child's cries sounding like a .
8. A female with retarded sexual development, sterile, and short in stature, and with webbing of the skin in the neck region has syndrome characterized by the presence of only one chromosome.
9. A person with the genotype of XXY is actually a . (male, female)
10. Trisomy of chromosome 21 results in a condition known as syndrome.
11. A simian palmar crease is one of several indications of syndrome.
12. Who determines the sex of a child in humans?
13. Are identical twins always the same sex? (yes or no)
14. Are males biologically stronger than females? (yes or no)

Exercises. Multiple Choice. Select the best answer.

1. Which of the following is a true statement?

   (1) Most red blood cells are spherical.
   

   (2) Attached earlobes are a recessive trait.
   

   (3) Most people have straight thumbs when hitchhiking.
   

   (4) A long, big toe length is a dominant trait.
   

   (5) More than one answer is correct.
   
   

2. This syndrome is a result of an extra chromosome 13.

   (1) Cri-du-chat
   

   (2) Down's syndrome
   

   (3) Patau
   

   (4) Edward's
   

   (5) Turner's
   
   

3. This syndrome results in microcephaly, saddle nose, and severe mental retardation, often with early death.

   (1) Cri-du-chat
   

   (2) Down's syndrome
   

   (3) Patau
   

   (4) Edward's
   

   (5) Turner's

4. Which of the following is a correct statement?

   (1) Males are biologically superior to females.
   

   (2) More females are born each year than males.
   

   (3) Many of a person's traits are not apparent.
   

   (4) The male contributes more to the child's make-up than the female.
   

   (5) More females exhibit hemophilia than males.

5. Which of the following are sex-linked traits?

   (1) male pattern baldness
   

   (2) hemophilia
   

   (3) color blindness
   

   (4) both 2 and 3 are correct
   

   (5) all of these