1. Linked genes are inherited together.
2. Males have the X and the Y chromosome; females have two X chromosomes.
3. The female is heterogametic in flies but homogametic in humans.
4. Color-blind daughter = 1/2
Color blind son = 1/2
5. This equalizes the number of active sex-linked genes in each cell. (Some people may argue that this might not be the total reason.)
6. The carrier X chromosome in some of her cells is the X that was not inactivated. Therefore, the trait is expressed in those cells. Therefore, she can experience symptoms.
7. The metacentric centromere for chromosome 3 is approximately in the middle of the chromosome. The acrocentric centromere for chromosome 22 is near the end of the chromosome.
8. See page 296.
9. Trisomy 21.
10. All definitions are in text.
11. Descriptions can be found in text
a. Triplo-X female
b. Turner syndrome female
c. Trisomy 21 female
d. Klinefelter syndrome male.
TO THINK ABOUT
1. Mendel's laws dealt with genes on separate chromosomes. Linked genes are on the same chromosome.
2a. Answers will vary but should include DNA samples from parents.
b. Answers will vary.
3a. Inactivation of the chromosome.
b. Answers will vary.
4. Probably mitosis without cytokinesis at about the four cell stage. (Other explanations are possible.)
5. Calico coloring is related to active/inactive X chromosomes. Males have only one and it stays active.
6. Any of several anomalies leading to excess height.
7a. Reciprocal translocation
b. See page 304.
c. Probably not because this translocation causes reproductive problems. However, it is possible, in which case either parent might also be a translocation carrier.
8. First question, which chromosome? Second question, how much?
9. The whole experiment was flawed because Jacobs did not test the non-prison population to see what the incidence of XYY males were found in the general populace.
10. Partial or complete inactivation of the Y chromosome
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