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R E V I EW E X E R C I S E S 1. A 23-year-old woman with sickle cell disease and her husband want to have a child, but worry that the child will be born with the disease. A. What is the mother’s genotype in terms of the sickle cell gene? Is she heterozygous or homozygous? B. If the husband is found not to have the sickle cell gene, what is the probability of their child having the disease or being a carrier of the sickle cell trait? 2. A couple has a child who was born with a congenital heart disease. A. Would you consider the defect to be the result of a single-gene or a polygenic trait? B. Would these parents be at greater risk of having another child with a heart defect, or would they be at equal risk of having a child with a defect in another organ system, such as cleft palate? 3. A couple has been informed that their newborn child has the features of Down syndrome. It was suggested that genetic studies be performed. A. The child is found to have trisomy 21. Use Figure 6-8 to describe the events that occur during meiosis to explain the origin of the third chromosome. B. If the child had been found to have the robertsonian chromosome, how would you explain the origin of the abnormal chromosome? 4. A 26-year-old woman is planning to become pregnant. A. What information would you give her regarding the effects of medications and drugs on the fetus? What stage of fetal development is associated with the greatest risk? B. What is the rationale for ensuring that she has an adequate intake of folic acid before conception? C. She and her husband have an indoor cat. What precautions should she use in caring for the cat? R E F E R E N C E S 1. Nassbaum RL, McInnes RR, Willard HF, et al. Thompson & Thompson Genetics in Medicine . 7th ed. Philadelphia, PA: Saunders Elsevier; 2007:33–94, 157–179, 359–389. 2. Pieper S, Rubin E, Strayer DS. Developmental and genetic diseases. In: Rubin R, Strayer DS, eds. Rubin’s Pathology: Clinicopathologic Foundations of Medicine . 6th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2012:213–266. 3. Kumar V, Abbas AK, Fausto N, et al. Robbins and Cotran Pathologic Basis of Medicine . 8th ed. Philadelphia, PA: Saunders Elsevier; 2010:135–182.