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Integrated Science II
Ch. 7 Explain
Name _______________________________
Period _______ Date _____________
More Genetics Problems
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1. In humans, hair type is an example of incomplete dominance. There are two versions of the hair type gene, curly (C)
and straight (S). If you have one of each allele (version of the gene), you get a mix of the two or wavy hair. So for hair
type, CC gives curly, CS gives wavy and SS gives straight hair.
If both parents have curly hair, fill in the Punnett Square to show
the hair types they could expect in their children.
a. Father’s genotype: _________
Mother’s genotype: _________
b. What % chance of could you expect in the offspring from this cross?
% Curly: _______ % Wavy: _______ % Straight: _______
2. The allele for normal hemoglobin can be represented as ‘H’. The allele for sickle cell anemia can be represented as ‘h’.
Heterozygous individuals produce both normal and sickled red blood cells and are resistant to malaria.
Fill in the Punnett Square to show the result of a cross where the father is
heterozygous for this disease and the mother actually has sickle cell anemia.
a. Father’s genotype: _________
Mother’s genotype: _________
b. What % chance of sickle cell anemia could you expect in the offspring from
this family?
% Normal: ______ % ‘Normal’, malaria resistant: ______ % Sickle cell: _______
3. How is Huntington’s disease inherited? ___________________________________________________________
Fill in the Punnett Square for a man who has Huntington’s disease (his own father didn’t have Huntington’s but his
mother did) and his wife who doesn’t have Huntington’s disease have kids.
a. Father’s genotype: _________
Mother’s genotype: _________
b. Offspring genotypes: _______% HH
_____% Hh
c. Offspring phenotypes: _____% Huntington’s disease
_____% hh
_____% Normal
4. Kurt who is red-green color-blind marries Ella who has normal vision but her father is red-green color-blind. Fill in the
Punnett square below to determine the chance of one of their children having red-green color-blindness.
XR = Normal, Xr = red-green color blindness
a. Kurt’s genotype: ___________
Ella’s genotype: ___________
b. What % chance of could you expect in the children in this family?
% Normal Male: ________
% Red-green color-blind male: ________
% Normal Female: _______ % Red-green color-blind female: _______
c. Can a boy inherit red-green color-blindness from his father? Explain.
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5. A man with type AB blood and a woman with type AB blood get married. Fill in the following Punnett square to show the
blood types they could expect for their kids.
a. Father’s genotype: _________
Mother’s genotype: _________
b. Offspring phenotypes: _____% A _____% B _____% AB _____% O
c. Suppose that one of the couple’s children needs an operation. This child has type B blood. Can the child safely
receive a blood transfusion from either parent? Explain.
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6. Is it possible for two people with type A blood to have a child with type O blood? Use a Punnett square to help explain
your answer.
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7. A man with type A blood, whose own mother had type O blood marries a woman with
type B blood whose own father had type AB blood. Fill in the following Punnett square
to show the blood types they could expect for their kids.
a. Father’s genotype: _________
Mother’s genotype: _________
b. Offspring phenotypes: _____% A _____% B _____% AB _____% O
8. Achondroplasia, a form of dwarfism, is caused by a dominant allele ‘A’. Embryos with the genotype ‘AA’ do not survive.
Individuals who are homozygous recessive for this trait are phenotypically normal. Suppose that two people with
achondroplasia get married and have children. Fill out the Punnett square to show what they might expect for their
children.
a. Mother’s genotype: _________
Father’s genotype: _________
b. Offspring genotypes: _______% AA
_____% Aa
_____% aa
c. Offspring phenotypes: _____% dwarf
_____% phenotypically normal
d. One of the children, who has a normal phenotype, marries a person who also has a normal phenotype. What
percentage of their children is likely to have achondroplasia? Explain.
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9.
In a species of chicken, feather color is a codominant trait. Heterozygotes (BW) are called “checkered” chickens because
they have both black and white feathers. If two checkered chickens are mated, what could their offspring look like?
a. Mother’s genotype: _________
10.
Father’s genotype: _________
b. Offspring genotypes: _______% BB
_____% BW
_____% WW
c. Offspring phenotypes: _____% Black
_____% Checkered
_____% White
In calico cats, hair color is X-linked. It is also a codominant characteristic. Cross a male black cat with a female calico cat
(XB = Black, XY = Yellow, XBXY = Calico). Fill in the following Punnett square to show the fur color they could expect for
their offspring.
a. Mother’s genotype: _________
b. % Black Male: ________
Father’s genotype: _________
% Yellow male: ________
% Black Female: _______ % Calico female: _______ % Yellow female: _______
c. Why is it not possible to have a calico male cat?
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