Question

Inheritance and Mutations in a Single-Gene Disorder (10pts - all questions worth 0.5pts) 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. Examining Mutations That Cause LCA Many genes contain instructions for making proteins, which have important functions in the body. Mutations, changes in a gene's DNA sequence, can affect these proteins and cause inherited diseases, such as LCA. Watch the short film Genes as Medicine until time 2:44. Figure 4 shows two illustrations from the film. Figure 4. Illustrations comparing unmutated and mutated, disease-causing copies of a gene, and their resulting proteins. Protein Protein Gene Mutation Based on the film, what is the difference between the two proteins shown in Figure 4? Consider what mutations Molly and her parents may have in the gene related to Molly's LCA. Using Figure 4 as a guide, draw the maternal and paternal versions of the chromosomes for Molly and her parents, showing the gene's two alleles and their resulting proteins for both of Molly's parents and Molly. Use the diagram you drew to explain why Molly's parents do not have LCA, but Molly does.

Answer 1

Leber Congenital Amaurosis (LCA), an inherited form of blindness result from mutations in at least 14 genes and affected Molly has a autosomal recessive pattern of inheritance as both of her parents doesn't get affected by the disease but simply acts as carrier. Therefore, both of her parents had a single faulty allele of a gene resulting from mutation and one normal allele. The one normal allele is sufficient for producing normal functional protein in both of them which is not the case with Molly as she inherited the two faulty allele of a gene each from one of her parents. Hence, the protein produced in Molly has lost its structure and therefore the function which contributes to the blindness which she develops.
Molly's Father Molly's mother ca) chomosome: - Mutated allele A VA - NO- Bo allele DU V Toon: Funcional Functional Molly chromosome Proton Non functional W - Mutated allele