Name:
Date:
HUMAN PEDIGREE WS
Standards: Genetics 2e, 2f, 2g, 3a, and 3c
Objectives:
 Students should be able to interpret a human pedigree.
 Students shall be able trace x-linked traits through a pedigree.
A sex-linked characteristic is determined by an allele that is
carried only on the X chromosome. The shorter Y chromosome
does not carry an allele for a sex-linked trait. Most sex-linked
traits are recessive. Since there is only one X in his genotype,
XY, a male who carries a particular recessive allele on the X
chromosome will have the sex-linked condition. A female who carries a
recessive allele in one X chromosome will not show the condition if there is a
dominant allele on her other X chromosome. She will express the recessive
condition only if she inherits two recessive alleles—one from each parent. Her
chances of inheriting the condition are far less compared with males.
One sex-linked trait is hemophilia, a condition in which the blood does
not clot properly. Common injuries and bruises can be fatal to a person who
suffers from hemophilia. Since men possess only one X chromosome (XY), they
are more likely to inherit the disease than women.
1. What is a sex-linked trait?
2. Can women and men both inherit SEX-LINKED TRAITS (yes or no)?
3. Who is more likely to inherit a sex-linked trait, Men or Women (circle)?
Explain?
HUMAN PEDIGREE
(Expressing Hemophilia)
Per.:
I
4. Study the pedigree and answer the following question (# 5-10).
5. Squares represent males . If the square is darkened, he has hemophilia
(genotype= XhY ); if clear he has normal blood clotting (genotype= XHY ).
a. How many males have hemophilia?
b. How many males do not have hemophilia?
6. Circles represent females. If it is completely darkened, she has hemophilia
(genotype= XhXh ); if clear she is normal for blood clotting (genotype= XHXH
).
a. How many females have hemophilia?
b. How many females are pure-bred dominant for normal blood
clotting?
7. Some circles are half shaded for females. Half shaded circles represent a
heterozygous condition for hemophilia where her genotype expresses one
dominant and one recessive trait (i.e.= XHXh). Females who are heterozygous
are called “carriers.” The females are normal, however they can pass the
recessive trait to their children.
a. How many females are “carriers” for hemophilia?
8. A marriage is indicated by a horizontal line connecting a circle to a square.
a. How many marriages are present?
9. Each generation is represented along with the offspring associated with each.
a. How many generations are present in this pedigree?
10. A line perpendicular to a marriage line indicates the offspring. The first
child is represented on the left and the last child is to the right.
a. How many children did the first generation have?
Name:
Date:
HUMAN PEDIGREE WS
Per.:
I
Applying the skill: Translate the following symbols into a genotype
and phenotype, and assess the health status of individuals with sexlinked traits.
Analysis: Use the pedigree above to answer questions #11-13
11. Why did family members in the second generation experience some
Symbol
Genotype
14.
form of hemophilia?
15.
16.
12.
a. How many children did couple 3-4 have?
b. Why did child #11 receive a recessive hemophilia trait and #13 did not?
17.
18.
13. Child #13 did not have hemophilia and the family history with hemophilia
could have ended with him. Why did his children end up with hemophilia?
Phenotype
Hemophilia,
Normal, or
Carrier.
Affected  or
NOT
Affected 
Name:
Date:
#11-18. The pedigree below is NOT
HUMAN PEDIGREE WS
I
STOP! Do not answer the following until question #191-18 has been
completed!
correct.
You will need to shade in the males and females correctly with
the information already given (Hint: Work bottom –up. #7 will
need to be shaded.
 Try to make the family as HEALTHY as possible  
Genotype
Genotype
Per.:
19.
(#) How many marriages?
20.
XY represents?
21.
(#) How many XHY?
22.
(#) How many XhY (Men with hemophilia)?
23.
XX represents?
24.
(#) How many XHXH?
1.
10.
25.
(#) How many XHXh “CARRIERS”?
2.
11.
26.
(#) How many XhXh (Women with hemophilia)?
3.
12.
27.
Y or N Carrier females XHXh are affected with sex-linked traits.
4.
13.
5.
14.
6.
15.
7.
XHXh “Carrier”
16.
8.
17.
9.
18.