Genetic Counseling Making a Pedigree By Diana L. Duckworth Rustburg High School Campbell County

Pedigree Female with trait Normal female Male with trait Normal male Mating (marriage?) Children, birth order left to right

Example Now do your own pedigree, showing those with whom you share genetic material.

Sex Linked Gene The y chromosome has very few genes Any gene on the X chromosome is sex linked If the phenotype is found predominantly in males, then it is sex linked If recessive, female must be homozygous to express the gene Any male possessing the allele will have the phenotype Example: albinism & hemophelia

Genetic Disease Sickle Cell Anemia – abnormal hemoglobin molecules; 1/500 African Americans; recessive Hypercholesterolemia – abnormal receptor for cholesterol; dominant; 1/500 Tay-Sachs – defective brain enzyme; recessive; 1/3500 in Ashkenazi Jews (children) Cystic Fibrosis – recessive; defective chloride ion transport protein; 1/2500 Caucasians Hemophilia – sex-linked recessive; blood clotting factor defective; 1/10000 Huntington’s Disease – inhibitor of brain cell metabolism; (middle age); dominant; 1/10,000