Chapter 22 - Chromosomal Basis for Inheritance

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It is recommended you read the section "How to Work Pedigree Charts" before working any exercises.

Terms to Know in This Chapter:

autosome (sing.) [AU toe zome]

allosome (sing.) [AL oh zome]

XX chromosomes

XY chromosomes

probability

product law of probability

Barr body

sex-linked

sex-limited

sex-influenced

holandric

dominant

recessive

What You Need to Know:

You should be able to:

1. distinguish between autosomes and allosomes,
2. explain what determines whether an individual will be male or female,
3. predict in a mating between a male and female, the probability of having a female child,
4. using the product law of probability, predict the odds of having teh first two children of a mating be male,
5. define sex-linked, sex-limited, sex-influenced, and holandric genes and give an example of each, and,
6. be able to interpret a pedigree chart and explain how to predict traits from one.

Exercises: Fill in the Blank.

1. In some domestic fowl (chickens) tail and neck plumage is often distinctly different in males and females. The genotype "HH" results in a condition known as "hen-feathering" in both males and females, "Hh" results in hen-feathering in both males and females, but "hh" produces hen-feathering in females, but "cock-feathering in males. Cock-feathering results in longer tail feathers and the "rooster" look in chickens. This is an example of inheritance. (sex-linked, sex-limited, sex-influenced, holandric)
2. Male pattern baldness is an example of inheritance. (sex-linked, sex-limited, sex-influenced, holandric)
3. Red/green color blindness in humans is an example of inheritance. (sex-linked, sex-limited, sex-influenced, holandric)
4. The probability that the first two children of a mating will both be females is .
5. A way to tell if you are looking a a female, is to view the white blood cell under a microscope and look for this structure.
6. The XX and XY chromosome may also be called while the other 22 pairs of chromosomes should be called .
7. Genes found on the "Y" chromosome are said to be .
8. What is the probability of producing a hemophiliac female child if the father is a hemophiliac and the mother is a carrier for the trait?

Exercises. Multiple Choice. Select the best answer.

1. Which of the following would you consider to be a sex-influenced trait?

   (1) hen-feathered in fowl
   

   (2) hemophilia

   (3) red-green color blindness

   (4) male pattern baldness

   (5) eye color
   
   

2. Which is a simple, autosomal dominant-recessive trait?

   (1) hen-feathered in fowl
   

   (2) hemophilia

   (3) red-green color blindness

   (4) male pattern baldness

   (5) eye color
   
   

3. Using the pedigree chart below, predict the type of inheritance for the trait.

   (1) autosomal dominant
   

   (2) autosomal recessive
   

   (3) sex-linked dominant
   

   (4) sex-linked recessive
   

   (5) both 1 and 3 are possibilities

4. Which of the following is indicative of females?

   (1) XX allosomes
   

   (2) Barr bodies
   

   (3) inactive X chromosome
   

   (4) all of the above
   

   (5) none of the above

5. If the probability of producing a male offspring is 1/2, what is the probability that the first three offspring will all be males?

   (1) 1/2
   

   (2) 1/4
   

   (3) 1/6
   

   (4) 1/8
   

   (5) none of the above