Chapter 15 - Human Genetics Disroders Notes

Chapter 15 - Human Genetics Disroders Notes - Human Genetic...

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Human Genetic Disorders R ECESSIVE H UMAN D ISORDERS [ Parents are generally unaffected [ Defective form of a normal trait. Generally, more serious phenotypic affect than dominant genes. [ Often arise from consanguineous matings. [ Heterozygotes normal Æ two unaffected parents can have affected offspring. [ Probability that child of two carriers will be affected is ¼. [ 2/3 of normal offspring from 2 carriers will also be affected. [ Can remain in population in heterozygote condition at high frequencies. Only a small number of homo-, recessive are affected. Ex.: [ Cystic Fibrosis (CF); autosomal recessive. [ Tay-Sachs; autosomal recessive [ Sickle-Cell; autosomal recessive [ Xeroderma pigmentosa; autosomal recessive. Defective DNA repair after ultraviolet radiation damage Æ malignant melanoma [ Albinism; autosomal recessive [ PKU; autosomal recessive [ Color blindness (X-linked recessive) Cystic Fibrosis [219700] : [ 1/2500 US Caucasians; 1/17,000 Blacks; 1/90,000 Asians [ Ineffective component of Na + /Cl - pump. Mutant gene affects glands that produce mucus, digestive enzymes and sweat. Release of excessively salty sweat an indicator of disease. [ Thick mucus clogs ducts for digestive enzymes Æ reduced effectiveness of digestion Æ malnutrition. Mucus also clogs reproductive ducts Æ infertility. [
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Chapter 15 - Human Genetics Disroders Notes - Human Genetic...

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