CHAPTER 12 Test Your Knowledge
Driving Question 1
How do chromosomes determine sex, and how does sex influence the inheritance of certain traits?
By answering the questions below and studying Infographics 12.1–12.5, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
Which of the following most influences the development of a female fetus?
a. the presence of any two sex chromosomes
b. the presence of two X chromosomes
c. the absence of a Y chromosome
d. the presence of a Y chromosome
e. either b or c
Why are more males than females affected by X-linked recessive genetic diseases?
If a man has an X-linked recessive disease, can his sons inherit that disease from him? Why or why not?
USE IT
Which of the following couples could have a boy with Duchenne muscular dystrophy (DMD)?
a. a male with Duchenne muscular dystrophy and a homozygous dominant female
b. a male without Duchenne muscular dystrophy and a homozygous dominant female
c. a male without Duchenne muscular dystrophy and a carrier female
d. a and c
e. none of the above
Predict the sex of a baby with each of the following pairs of sex chromosomes. Use your answer to check your answer to Question 1.
a. XX
b. XXY
c. XY
d. X
Consider your brother and your son.
a. If you are female, will your brother and your son have essentially identical Y chromosomes? Explain your answer.
b. If you are male, will your brother and your son have essentially identical Y chromosomes? Explain your answer.
A wife is heterozygous for Duchenne muscular dystrophy alleles and her husband does not have DMD. Neither has any other notable medical history. What percentage of their sons, and what percentage of their daughters, will have:
a. Duchenne muscular dystrophy (which is determined by a recessive allele on the X chromosome)
b. an X-linked dominant form of rickets (a bone disease)
Driving Question 2
Some traits are not inherited as simple dominant or recessive inheritance patterns. What are some of these complex inheritance patterns?
By answering the questions below and studying Infographics 12.6–12.11, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
What aspects of height make it a polygenic trait?
Which of the following inheritance patterns includes an environmental contribution?
a. polygenic
b. X-linked recessive
c. X-linked dominant
d. multifactorial
e. none of the above
What is the difference between polygenic inheritance and multifactorial inheritance?
How does incomplete dominance differ from co-dominance?
If you are blood type A-positive, to whom can you safely donate blood? Who can safely donate blood to you? List all possible recipients and donors and explain your answer.
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USE IT
If two women have identical alleles of the suspected 20 height-associated genes, why might one of those women be 5 feet 5 inches tall and the other 5 feet 8 inches tall?
Look at Infographic 12.11. How do the data given support the hypothesis that both genes and the environment influence at least some cases of clinical depression?
Look at Infographic 12.11. At approximately how many stressful experiences does the homozygous short-allele genotype begin to influence the depression phenotype?
From what you have read in this chapter, how can you account for two people with the same genotype for a predisposing disease allele having different phenotypes?
MINI CASE
A serious car crash on a freeway has resulted in multiple injuries causing substantial blood loss in three members of a family—a mother, a father and their 2-year-old daughter. The local blood bank will be challenged to supply blood, as their supplies of every blood type were drained after the roof of a shopping plaza collapsed the week before and many transfusions were required.
a. The EMTs must give blood immediately to all three members of the family. What blood type should they use (consider both ABO blood type and Rh factor)? Explain your answer.
b. Both parents have a blood donor card in their wallets. The mother is O-negative and the father is A-positive. From this information, what (if any) additional blood types (beyond your answer to part a) can be given to either parent? Explain your answer.
c. Does knowing the parents’ blood types allow you to infer enough information about the daughter’s possible blood type to use a different blood type for her transfusion? Why or why not? (Hint: Consider possible blood types for the daughter and the implications of, for example, using A-negative donor blood. Could you guarantee that this would be safe?)
Driving Question 3
How do numerical abnormalities of chromosomes occur, and what are the consequences of these abnormalities?
By answering the questions below and studying Infographics 12.12 and 12.13, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
What is the normal chromosome number for each of the following?
a. a human egg
b. a human sperm
c. a human zygote
When looking at a karyotype, for example to diagnose trisomy 21 in a fetus, is it possible to use that analysis also to tell if the fetus has inherited a cystic fibrosis allele from a carrier mother?
USE IT
Which of the following can result in trisomy 21?
a. an egg with 23 chromosomes fertilized by a sperm with 23 chromosomes
b. an egg with 22 chromosomes fertilized by a sperm with 23 chromosomes
c. an egg with 24 chromosomes, two of which are chromosome 21, fertilized by a sperm with 23 chromosomes
d. an egg with 23 chromosomes fertilized by a sperm with 24 chromosomes, two of which are chromosome 21
From what you have read in this chapter, which of the possibilities in Question 20 is most likely? Explain your answer.
BRING IT HOME
What factors would lead you to consider prenatal genetic testing? In your opinion, what is the value of having this information?
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INTERPRETING DATA
The graph at right shows the average (“Mean”) age of women who had children with trisomy 21 (“Cases”), of those who did not (“Controls”), and the average age of women giving birth in the population. The data are presented for 15 years.
a. In general, how does the age (at time of birth) of women giving birth to a baby with Down syndrome compare to the age of women giving birth to a baby without Down syndrome?
b. During which year was the average age of the cases closest to the average age of the controls? How close were the average ages in this year?
c. During which year was the average age of the cases the most different from the average age of the controls? How different were the average ages in this year?
d. Using the data points for each year over this 15-year period, calculate the overall average age of women having babies with Down syndrome, and the overall average age of women having babies who do not have Down syndrome.