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Molecular Basis of Heredity: Part 3. Genetic Variation

Author(s): Raye L. Alford, PhD

Human Genetic Disorders (II)

The genetic location of the gene(s) altered in association with a genetic disorder affects the pattern of inheritance of the disorder (the way a disease is inherited in a family). The pedigree shown in this slide illustrates an autosomal dominant disorder caused by mutation of a single gene that is being passed from one generation to the next throughout a family. Knowing the pattern of inheritance of the disorder allows prediction of genetic risks for family members. Knowing the gene involved in the disorder allows genetic testing to identify individuals at risk for the disease or for passing the disease gene to their children. In pedigree drawings, boxes are males, circles are females. Shaded shapes are affected individuals, open shapes are unaffected individuals. The diamond at the bottom of the pedigree represents a fetus of unspecified gender. In the autosomal dominant pedigree drawn here, the fetus would be expected, prior to genetic testing, to have a 50% chance of inheriting the disease gene. If a genetic test were available for the disorder in question, the test could determine whether this fetus inherited the disease-associated copy of the gene or the normal copy of the gene from his/her affected mother.