Biology
Name: ___________________________
Genetics Problems
1. Albinism is a condition in which a person does not make skin pigment. It is caused by a recessive
allele. Normal skin pigment is the dominant trait. Cross a homozygous pigmented person with
an albino. What are the phenotype and genotype probabilities of their children?
A
a Aa
a Aa
A
Aa
Aa
Phenotype – 4 pigmented
Genotype – 4 Aa
2. Cross two heterozygous pigmented parents. What are the phenotype and genotype probabilities
of their children?
A
A AA
a Aa
a
Aa
aa
Phenotype – 3 pigmented: 1 albino
Genotype: 1 AA:2Aa:1aa
3. Cross a heterozygous normally pigmented parent with an albino parent. What are the
phenotype and genotype probabilities of their children?
A
a Aa
a Aa
Phenotype – 2 pigmented: 2 albino
Genotype: 2Aa:2aa
a
aa
aa
4. Brown eyes are dominant to blue eyes. A brown eyed man marries a blue eyed woman. The first
child is blue eyed. What is the man’s genotype? Show a punnett square to prove this.
B
b Bb
b Bb
b
bb
bb
Man’s genotype is Bb
5. Tall pea plants are dominant to short pea plants. Two heterozygous tall pea plants were crossed
and they produced 100 seeds. What types of pea plants are EXPECTED to grow from these 100
seeds? List the phenotype probabilities.
T
T TT
t Tt
t
Tt
tt
3 tall: 1 short
6. Mr. A has blue eyes, but both his parents have brown eyes. Mrs. A has brown eyes; her mother
has brown eyes but her father has blue eyes. Mrs. A has seven brothers and sisters, all of whom
have brown eyes. Indicate the genotype of the following”
Mr. A ____bb___________
Mrs. A ___Bb______________
Mr. A’s father __Bb_________
Mrs. A’s father ____bb____________
Mr. A’s mother __Bb_________
Mrs. A’s mother _BB could be Bb__________
What proportion of Mr. and Mrs. A’s children will have brown eyes? ___1/2__________
B
b Bb
b Bb
b
bb
bb
Biology
Sex Linkage Problems
Name: _____________________________
1. In fruit flies, red eye color (R) is dominant over white eye color (r), and the trait is linked on
the X chromosome. What genotypes and phenotypes will result from a cross between a redeyed male and a heterozygous red-eyed female?
XR
Xr
XR
XRXR
XRXr
Y
XRY
XrY
Phenotypes – 2 red eyed females: 1 red eyed male: 1 white eyed male
2. Hemophilia is sex linked to the X chromosome, and it is recessive genetic disorder. A carrier
woman mates with a man who has hemophilia. What are the odds of having a child with
hemophilia?
XH
Xh
Xh
XHXh
XhXh
Y
XHY
XhY
50% chance of having a child with hemophilia
3. In humans, color blindness (c) is recessive to normal vision (C) and is sex-linked. Two parents
with normal vision have a color -blind son. What is the probability that their next child will
be a color blind daughter?
XC
Xc
XC
XCXC
XCXc
Y
XCY
XcY
Cannot have a color blind daughter since father is not color blind. Females need 2
recessive genes to be color blind.
4. Why are males more afflicted with recessive sex linked traits than females?
Males only have 1 x chromosome.
5. Can a male transmit a sex linked trait on the X chromosome to his son? Explain.
No, the male gives the Y chromosome to his son
Biology
Name: _______________________________
Blood type problems
1. Cross a homozygous Type A person with a heterozygous Type B person. Show all possible results
for their children.
B
A AB
A AB
O
AO
AO
2. Cross a Type AB person with a Type O person. Show all possible results for their children.
A
O AO
O AO
B
BO
BO
3. A woman with type AB blood marries a man with type A blood. His mother had type O blood.
What blood type is not likely to occur among the couple’s children. Explain by showing work.
A
A AA
O AO
B
AB
BO
Will not have a child with OO blood
4. A man has type A blood and his wife has Type B blood. A physician types the blood of their 4
children and is amazed to find one of each of the 4 blood types among them. Explain how this
can happen. Show work.
A
B AB
O AO
O
BO
OO
Biology
Incomplete Dominance
Name: ___________________________
1. When white chickens (W) are mated with black chickens (W’), the baby chicks are white and
black speckled (WW’). Cross two speckled chickens and list the genotype and phenotype
probabilities of their offspring. Show the punnett square.
W
W WW
W’ WW’
W’
WW’
W’W’
Genotype – 1 WW:2WW’:1W’W’
Phenotype – 1 white:2 speckled: 1 black
2. Cross a speckled chicken with a white chicken and list the genotype and phenotype
probabilities of the baby chicks. Show the punnett square.
W
W WW
W’ WW’
W
WW
WW’
Genotype – 2 WW:2WW’
Phenotype – 2 white:2 speckled
3. When yellow guinea pigs (Y) are crossed with white guinea pigs (y), cream colored offspring
are produced (Yy). Can a pet store owner mate a cream colored male and a white female to
obtain yellow guinea pigs? Show your work.
Y
y Yy
y Yy
y
yy
yy
No. Half will be cream and half would be white.
4. A cross between round radishes (R) and long radishes(r) produces oval radishes (Rr). In a
radish breeding experiment, the following radishes were obtained:
25 long radishes: 52 oval radishes:26 round radishes
Determine the probable genotypes and phenotypes of the parent radish plants. Show work.
R
R RR
r Rr
Genotype – 1RR:2Rr:1rr
Phenotype: 1round:2 oval:1 long
r
Rr
rr