Part I. Textbook Questions
Chapter 3:
8. Describe briefly:
a. The genotype of a person who has sickle-cell anemia.
b. The genotype of a person with a normal phenotype who has a child with sickle-cell anemia.
c. The total number of different alleles of the p-globin gene that could be carried by five children with the same mother and father.
12. One of your fellow students tells you that there is no way to know that the spotted and dotted patterns on the lentils in Fig. 3.4a (p. 48) are due to codominant alleles (cs and CD) of a single gene C. He claims that spotting could be controlled by gene S, with a completely dominant allele S that directs spotting and a recessive allele s that directs no spots. Likewise, he claims that dotting could be controlled by a separate gene D, with a completely dominant allele D that directs dotting and a recessive allele d that directs no dots. Is he correct, or does the information in Fig. 3.4a argue against this idea? Explain.
14. In clover plants, the pattern on the leaves is determined by a single gene with multiple alleles that are related in a dominance series. Seven different alleles of this gene are known; an allele that determines the absence of a pattern is recessive to the other six alleles, each of which produces a different pattern. All heterozygous combinations of alleles show complete dominance.
Part II. Short Answer
In your own words (please do not copy the wording of the article), use the article Sickle Hemoglobin (Hb S) Allele and Sickle Cell Disease : A HuGE Review to answer the questions below:
1. What are the at-risk genotypes associated with Hb S? Use this article or Figure 3.9 to help you.
2. What is the mode of inheritance?
3. Briefly list the symptoms individuals who have 2 copies, or 1 copy of the Hb S variant experience?
4. What is the difference in phenotype between normal carrier, diseased individuals?
5. Why has the frequency of individuals of African Mediterranean ancestries maintained the sickle cell trait?
6. Create a punnett square using 2 carriers of the sickle cell allele. Include the phenotypic and genotypic ratios.