Sasha Preston - SingleGeneDisorder-StudentHO-act12.pdf - Inheritance and Mutations in a Single-Gene Disorder Activity Student Handout INTRODUCTION Some

Sasha Preston - SingleGeneDisorder-StudentHO-act12.pdf -...

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Genetic Disease September 2019 Page 1 of 5 Activity Student Handout Inheritance and Mutations in a Single-Gene Disorder INTRODUCTION Some diseases are caused by the environment. For example, exposure to chemicals or extremely bright lights can cause certain forms of blindness. But other forms of blindness are inherited, meaning that they are passed on from one generation to another. In this activity, you will learn about a young woman, Molly Troxel, who has an inherited form of blindness called Leber congenital amaurosis (LCA). The activity explores how LCA is inherited, the mutations that cause it, and how the disease can be treated to help Molly and other patients. PART 1: Determining LCA’s Pattern of Inheritance Watch the short film Genes as Medicine until time 1:42 . You will meet Molly and learn about what causes her blindness. Use what you learn from the film to answer the following questions. 1. Imagine you’re a doctor treating a patient with severe vision issues. What questions might you ask to determine whether these issues are more likely to be inherited or caused by environmental factors? Some inherited diseases, including LCA, may be caused by mutations in a single gene. Pedigrees can be used to determine the patterns of inheritance for these diseases. In a 1998 study, scientists analyzed a series of pedigrees showing the family histories of LCA patients. Some of their pedigrees are shown in the following figures. Squares represent males, circles represent females, and shading indicates that an individual has LCA. Figure 1. A pedigree of a family that has individuals with LCA. Adapted from Morimura et al. (1998). Figure 2. Two pedigrees of families that have individuals with LCA. Adapted from Morimura et al. (1998). 2. Based only on the pedigree in Figure 1 , can you determine whether LCA is or isn’t inherited according to an autosomal dominant, autosomal recessive, or X-linked recessive pattern? Explain your answer.
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