Download Sex linked traits / multiple allele assignment

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Sex linked traits and multiple allele problems
Use the following information to help with numbers 1-6. Circle the
best answer.
In humans, the gene for normal color vision (C), is dominant to the
gene for red-green colorblindness, (c). This trait is sex-linked.
1. The parents of a color-blind daughter could have which of the
following genotypes?
A. XCXc and XCY B. XcXc and XCY C. XCXc and XcY
D. XCXC and XcY
2. A heterozygous female marries a color-blind male.The chance of having a colorblind son is
A. 50%
B. 25%
C. 100% D. 0%
3. Both a man and his wife are color blind. The chance that their first child will be a son with
normal vison is…
A. 50%
B. 25%
C. 100%
D. 0%
4. A female who is homozygous for normal vision marries a color-blind male. The chance that a
daughter they produce will be color-blind is…
A. 50%
B. 25%
C. 100%
D. 0%
5. A girl with normal vision has a color-blind father. If the girl marries a color-blind
male, the chance of their first child being a color blind son is…
A. 50%
B. 25%
C. 100%
D. 0%
6. A color-blind female marries a normal vision male. The expected phenotypic ratio among
their offspring is…
A. ½ daughters with normal vision : ½ sons with normal vision
B. ½ color-blind daughters : ½ color-blind sons
C. ½ color-blind daughters : ½ sons with normal vision
D. ½ daughters with normal vision : ½ color-blind sons
7.-15. Indicate whether each of the following statements is TRUE or FALSE. If the statement is
false, correct the bold face underline phrase in a way so to make it true.
In fruit flies, the gene for red eye color, (R), is dominant to the gene for white eye color, (r). The
trait is sex-linked. A red-eyed male was bred with a heterozygous red-eyed female.
7. The gene for eye color is carried on the X chromosome
8. The male’s genotype is XRYr
9. The female’s genotype is XRXr
10. Half the gametes produced by the female should contain Xr
11. All the gametes produced by the male should contain Yr
12. Of the offspring produced, all females are expected to have red eyes.
13. Of the the offspring produced, all males are expected to have white eyes.
14. Red-eyed male offspring must have the genotype XrY
15. Female offspring produced from this cross could have the genotype XrXr
16. – 21. The diagram below is called a PEDIGREE. Pedigrees are used to track traits down through a
series of generations and can be useful in a number of different ways. This pedigree shows how the trait
of color blindness is carried down through three generations. You need to know that color blindness is a
recessive, sex-linked trait.
Each symbol is a person; circles are females and squares are male. Persons 1 and 2 are the
original parents. Marriages are indicated by striped lines and children are shown by solid bars. If a symbol
is shaded, the person is color blind. If a person is unshaded, they have normal vison (but could be a carrier
of the color blind allele). Use this pedigree to answer questions 16 – 21. Use (C) for normal vison and (c)
for color blindness.
16. The genotype of Person 1: _______
17. The genotype of Person 2: _______
18. The genotype of Person 10: ______
19. The genotype of Person 14: _______
20. Can you tell with certainty what the genotype of
Person 6 will be? Explain.
21. The pedigree shows Person 12 as being unshaded.
Is this correct? Explain.
Traits with more than two forms
22.- 28. Indicate whether each of the following statements is TRUE or FALSE. If the statement is false,
correct the bold face underline phrase in a way so to make it true.
Suppose that when Vincent gets to Titan he finds creatures with three genes that control
hair color. The gene for green hair, (G), is dominant to both the gene for purple hair,
(P), and the gene for orange hair, (O). The gene for purple hair is also dominant to the
gene for orange hair.
22. A creature with orange hair must have the genotype OO.
23. All creatures with purple hair must be have the genotype, PP.
24. All creatures with green hair are either GG or GO.
25. All offspring produced by two orange – haired parents are expected to have orange hair.
26. If two green-haired parents produce an offspring that has orange hair, then each parent must have an
O allele.
27. If a purple-haired parent and an orange haired parent produce all purple-haired offspring, then the
purple-haired parent is most probably heterozygous.
28. All the offspring produced by two green-haired creatures always are expected to have green hair.
29. A man has type A blood and his wife has type B blood. A physician types the blood of their
four children and is amazed to find one of each of the four blood types among them. Explain
how this could happen by telling me the genotypes of the parents and their four children.
30. Hemophilia is a sex-linked, recessive trait. A man, who is a hemophiliac, and a
woman, who is a carrier of the condition, want to have children. Although there are
effective treatments for this disease, they are still concerned about having children that must
deal with this life long illness. How would you counsel them? Your explanation can be in
the form of a Punnett square that shows the probable outcomes their children would show.