Download sexlinkage practice14

PEDIGREE WORKSHEET
Genes which are carried on the X chromosome are said to be sex-linked. It is easy to spot
recessive defects in genes located on the X chromosome because the genes are expressed more
frequently in males. This occurs because males normally have only one X chromosome. Males therefore
have all genes located on the X chromosome expressed: In order for a female to exhibit the recessive
trait, she must carry two recessive genes; one on each X chromosome, If a femalecan-ies 0nly one
recessive gene on one x chromosome, she is known as a carrier of the trait. She may then pass this gene
on to her offspring. Hemophilia or "bleeder's disease" is a sex-linked disorder.
The recessive genes cause the factor(protein antihemophilic factor)-to-be' ÿoÿS,ÿitlg. Because of
the missing factor, people who have hemophilia can bleed to death from even the smallest cut. Bumps
and bruises can cause internal bleeding. Injection of AHF extracted from donated blood can be used to
relieve most serious effects of the disease, Many hemophiliacs contracted the AIDS virus in the early
1980's because of the tainted blood transfusions they must receive in order to survive.
Hemophilia in the royal families of
Europe. This partial pedigree traces the
.sex-linked disease from Queen Victoria
through three generations of European
dynasties. Queen Victoria had nine
children, t'wenÿ-six grandchiktren,
GD-Queÿn
Victoria
and thizty-four greatgrandchildren;
only the aft'licted individuals and thei=
direct ancestors are shown here.
(ÿ Female carrier
Albert
[] tÿfafe hemophiliac
OÿJ Normal individual
Victoria Frederick I1[
Alice
Eouis IV
Prince,,s
(Hesse)
of Waldÿc]
Leopold
I B,.tÿenberg
Wilhelm II
(Germ,my)
I lenry ÿe
l:rÿdurick Afexandra Nidlol,ÿ II
(died a! 3)
Waldemar Henry
(died at 56) (died at 4)
Alice
F-.'ÿ r I LÿI'
Atltlolÿe
66 66,,,
o
=-"1 (murdered)
Ale is ÿ
ÿÿ(died
Rupert
at 21)
AJfonso Fonzalo
(died at 31) (died at 20)
.€.L_
With the symbols in mind, the following questions can now be answered.
1. List Queen Victoria's children that are shown on the pedigree.
2. Tell which of her children are carder females and which are hemophiliac males.
3. Queen Victoria's daughter, Alice, married Louis IV of Hesse, and they had three children. List their
children and tell which are carrier females and which are hemophiliac males.
4, Queen Victoria's granddaughter, Alexandra, married Nicholas II, Czar of Russia. Who was their only
son? Did he have hemophilia?
5, Queen Victoria's son, Leopold, had one daughter. What was her name? Who did she inherit the gene
from? Was she a carrier female?
The next series of questions requires theuse. ' -"- ( -{-'°f symbols to calculate probabilities or explain how a gene
was inherited
.....
.ÿ
XX
Normal female
XX
Carder female
XY
Normal male
XY
Hemophiliac male
Use Punnett Squares to explain answers to the following questions. Remember Punnett Squares may be
used to calculate probabilities of inheritance. Sex-linked traits are handled the same way as nonsexlinked traits.
6..Would it be better for Leopold to have only sons or only daughters?
7. What is the probability that the daughters of Czar Nicholas II of Russia and Alexandra were carders?
(Remember we do not know for sure.)
8. Some of Queen Victoda's children did not have the disease nor were they carriers of the disease.
Explain why.
Class
Name
Date
CHAPTER 11
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SKILL ACTIVITY--
Human Heredity
interpreting diagrams
Section 11-3
Applied Genetics
A. Duchenne muscular dystrophy is a deadly disorder in which the muscles grow progressively
weaker. The disease is caused by a recessive gene on the X chromosome. The pedigree chart
below illustrates the inheritance of this gene. Use the chart to answer the questions that follow.
Key:
C
©
[3
@
D
Normal female.
Normalmale
Carrier female
Female with
disorder
J
()
Male with
disorder
1
1, Is Duchenne muscular dystrophy more likely to occur in males or in females? Explain your answer,
?
2. Individual H is a female with this disorder. Explain how she inherited this disease,
3. Individual K has this disorder, yet his father did rÿot. Explain how this is genetically possible,
4. Individual G does not have the disease, yet his mother was a carrier and his father had the disease.
Explain 'how this is possible.
© Prentice-Hall, Inc.
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5, Why is the genotype of the father unimportant when investigating sex-linked traits inherited
by male offspring?
B. Huntington disease, a disease of the nervous system, is caused by an autosomal dominant
gene. The pedigree chÿt below illustrates a family with individuals who have Huntington
disease. Use the chart to answer the questions that follow.
A
B
Key:
Female
Male
C
• Huntington
H disease
J
.,..,,
)
h Normal gene
6. What is the probable genotype of individual D? Explain your answer.
7, What are the probable genotypes of individuals H and I? ,Explain your answer.
8. What is the probability that N will not have Huntington disease?
9, Which individuals can be determined to have Huntington disease?
10. Identify the individuals whose genotypes cannot be determined without more information.
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© Prentice-Hall, Inc.
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