You'll play the role of genetic counselor. A couple with a family history of Duchenne muscular dystrophy has come to you to determine the chances of passing on the disease. Read the Family History and construct a pedigree to analyze the inheritance pattern for Duchenne muscular dystrophy and advise this family.
Family History: George and Vanessa are recently married and plan to have children. George's mother and father show no symptoms of muscular dystrophy, but his brother has the disease. George's brother is married and they have a son who does not have muscular dystrophy. Vanessa's mother shows no symptoms of muscular dystrophy and there is no history of the disease on her father's side of the family. However, Vanessa's maternal grandfather (her mother's father) had muscular dystrophy. Vanessa's fraternal grandfather (her father's father) showed no symptoLindms of muscular dystrophy, but she has no information about her grandfather's parents or siblings to determine if this side of the family has a history of the disease. Vanessa also has a brother and two sisters, none showing symptoms of the disease.
Once the pedigree is assembled, label the genotypes of each individual. Use the proper designation for X-linked alleles in which a capital X with a superscripted letter represents the gene locus. Use a capital "D" in the superscript (XD) to represent the dominant form of the allele and a lower case "d" in the superscript to represent the recessive form of the allele (Xd). Remember to include a Y chromosome for the males! If you are unsure of the genotype, label the individual with a "?" in the superscript position. Once the pedigree is assembled, label the genotypes of each individual. Use the proper designation for X-linked alleles in which a capital X with a superscripted letter represents the gene locus. Use a capital "D" in the superscript (XD) to represent the dominant form of the allele and a lower case "d" in the superscript to represent the recessive form of the allele (Xd). Remember to include a Y chromosome for the males! If you are unsure of the genotype, label the individual with a "?" in the superscript position.