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Biology 240
Clark College
Kibota 1
Name ______________________________
Genetics Problem Set (10 points)
1.
Explain why, in humans, many traits, e.g., albinism, blue eyes, and phenylketonuria, skip
generations while traits such as polydactyly, free earlobes, and A and B blood groups do not.
2.
Suppose there are two alleles for a gene. How can you tell which allele is dominant and which is
recessive?
3.
What is meant by the term “heterozygous”?
4.
Cystic fibrosis is an autosomal recessive disorder. Joe and Sara are both carriers of cystic fibrosis.
Sara is pregnant with their first child.
a.
What is the probability that this child develops cystic fibrosis?
b.
What is the probability that this child is a carrier?
c.
Assume their first child is normal (not a carrier). What is the probability that their second
child is normal (not a carrier)?
5.
Sam has type A blood. Rachel has type B blood. "Their" daughter, Allison, has type B blood. Can
Sam be the biological father of Allison? If Sam is the biological father, draw the pedigree and
indicate the genotypes and phenotypes of each individual.
6.
Frank has Red-Green Colorblindness (RGCB), an X-linked recessive trait. Joanne has normal
vision. What is the probability that their daughter, Samantha, has RGCB? What is the probability
that their son, Andrew, has RGCB?
7.
Dolores and John just became the proud parents of a baby boy Phillip. Jackie (John’s sister) died of
the rare autosomal recessive trait, Caterpillar Inversion Syndrome (CIS, which kills affected
individuals by the age of three). What is the probability that Phillip dies of CIS? What is the
probability that Phillip is a carrier of CIS?
8.
What is X-inactivation? How does X-inactivation lead to the mosaic coat coloration of Calico cats?
9.
You are interested in the inheritance of two traits. The first trait is nose shape (people either have
long noses (dominant) or short noses (recessive). The second trait is hair thickness (people either
have thin hair (dominant) or thick hair (recessive). Suppose different genes govern these traits and
the genes are unlinked. If a doubly heterozygous man marries a doubly heterozygous woman, what
is the probability of producing a child who has: (1) a long nose and thin hair; (2) a long nose and
thick hair; (3) a short nose and thin hair; (4) a short nose and thick hair?
10.
Suppose the two genes in question 9 are tightly linked and that both the man and the woman had
moms with short noses and thick hair. What is the probability of producing a child who has: (1) a
long nose and thin hair; (2) a long nose and thick hair; (3) a short nose and thin hair; (4) a short
nose and thick hair?
Biology 240
11.
IIA
Clark College
Kibota 2
In the human pedigrees illustrated the rare traits (represented by solid squares and circles) are
determined by alleles of single genes. For each pedigree:
a.
State whether the trait is autosomal or sex-linked and dominant or recessive.
b.
Determine the genotypes for each individual in each pedigree.
IA
IB
IIB
IIC
IIIA
IID
IIE
IIIB
IC
ID
IIF
IIG
IIH
IIID
IIIC
IB
IIA
IIB
IIC
IIIA
IID
IIIB
IIE
IIIC
IC
ID
IIF
IIG
IIID
IIH
Biology 240
IIA
Clark College
Kibota 3
Type AB
Type A
Type B
Type A
IA
IB
IC
ID
IIB
IIC
IID
IIE
IIF
IIG
Type AB
Type O
Type B
Type AB
IIH
What is the probability that individual IIH has type A blood?
What is the probability of individuals IID and IIE producing a child with type AB blood?
IA
IIIA
IIA
IIB
IIIB
IIIC
IVA
IB
IIC
IIID
IVB
IID
IIE
IIF
IIIE
IIIF
IIIG
IVC
IVD
IIIH