Pedigree Analysis Question Sheet
Question A
1.
2.
I
3.
4.
II
5.
6.
7.
8.
III
11.
9.
IV
10.
V
In the above pedigree, the affected individuals are shown shaded. None of the marriage partners
from outside these two families are heterozygous for the trait.
1. How is this particular trait inherited?
2. How many offspring are shown in the second generation?
3. If individual #10 mated with individual # 11, what are the chances of them producing an
offspring who is affected?
4. Indicate the genotypes of individuals # 1  10. (Write clearly above the number.)
(Allow the dominant trait to be “A” and the recessive trait to be “a” – NOTE: Some may have
two possible genotypes)
Pedigree Analysis Question Sheet
Version B
The following pedigree represents the inheritance pattern for the sex-linked, recessive trait colourblindness in humans. The person making this pedigree did NOT identify the carriers of the trait, just
those with or without colour blindness. You have to identify the genotypes of all individuals, by writing
the genotype clearly above the number. To do this you will use the allele symbols XB for normal colour
vision and Xb for the colour-blindness. You must also use the appropriate symbols for the genders. Fill
in the genotypes of each of the 23 individuals shown. If the complete genotype can not be determined
from the data provided then the symbol X—MUST be used for the unknown allele.
1.
5.
2.
6.
7.
12.
18.
3.
13.
19.
8.
14.
20.
9.
4.
10.
15.
21.
16.
11.
17.
22.
23.
Pedigree Analysis Question Sheet
Version C
Pedigree A
Pedigree B
Pedigree C
Pedigree D
Pedigree E
Possible Inheritance patterns:
Autosomal recessive
Autosomal dominant
X-linked recessive
X-linked dominant
Y-linked
1. For each of the pedigrees above, indicate which of the 5 inheritance patterns are possible (there
may be more than one possible). Explain your reasoning in each case.
2. Give the genotype for each of the affected individuals in pedigree C.
Longer Answer Questions
Pedigree Analysis Answer Sheet
Version A
1. The trait is autosomal recessive
2. Six offspring are shown in the second generation
3. There is a 25% chance
4.
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
xi.
Aa
Aa
AA
aa
Aa
Aa
Aa
Aa
Aa or AA
aa
AA or Aa
Longer Answer Questions
Pedigree Analysis Answer Sheet
Version B
One mark for each genotype, and one mark for each explanation.
#1
XBY
male and does not have trait
#4
XBXb
female and must be heterozygous as one of her sons has trait
#7
XBX--
female and can not tell if she is homozygous or heterozygous must use X—
#9
XbXb
female and must be homozygous recessive as she has the trait
#14.
XBXb
female and must be heterozygous as mother was XbXb and father was XBY
#18.
XBXb
female and must be heterozygous as she gets Xb from father but does not have the
trait
#21
XbY
is male and has the trait
Longer Answer Questions
Pedigree Analysis Answer Sheet
Version C
1. Pedigree A 
Autosomal Recessive
X-linked Recessive
Neither parent has the trait but one offspring
expressed it
Neither parent has it but one SON expressed it
Pedigree B 
X-linked Recessive
Both of the daughters express the trait, neither
SON does, both parents have it
Pedigree C 
Autosomal Recessive
Neither parent expresses the trait but one son
and one daughter express the trait
Pedigree D 
X-linked dominant
Both daughters express the trait, inherited from
the fathers affected X chromosome, neither son
expresses the trait
Only the daughters inherited the faulty chromosome
from the father by chance
Autosomal Dominant
Pedigree E 
Y-linked
Autosomal Dominant
Only the males in the family are affected by the
disorder.
Only the sons inherited the faulty chromosome from
the father by chance
2. Let ‘A’ stand for the dominant allele and ‘a’ stand for the recessive allele for this gene.
The affected individuals will be homozygous recessive for the trait
Genotype = aa