Orofacial Genetics for Dentists Part 2 PDF

Orofacial Genetics for Dentists Part 2 Farhad Khosrow Shahian, DDS PhD  Inheritance – Single gene disorders Sex-Linked inheritance – X Linked – Y Linked  Inheritance – Single gene disorders Female must be homozygous Male is hemizygous (since only 1 X c...

Orofacial Genetics for Dentists Part 2 Farhad Khosrow Shahian, DDS PhD  Inheritance – Single gene disorders Sex-Linked inheritance – X Linked – Y Linked  Inheritance – Single gene disorders Female must be homozygous Male is hemizygous (since only 1 X chr.) Eg – Haemophillia. Females with hemophillia – XO (Turner’s syndrome) – Homozygous – Mutation during gametogenesis Hemophilia A – X-linked Recessive Factor VIII deficiency Bleeding with minimal trauma, fails to clot Bleeding into joints – painful, debilitating Require factor replacement prior to dental procedures associated with bleeding Queen Victoria  Inheritance – Single gene disorders X linked dominant – Similar to autosomal dominant – X-linked dominant hypoplastic amelogenesis imperfecta – Hypophosphatemia – More severe form in males, females milder No male to male transmission  Hypophosphatemia X-linked dominant inheritance Recurrent spontaneous dental abscess formation affecting multiple non-carious primary teeth/permanent dentition Large pulp chambers, dentinal clefts, taurodontism Skeletal anomalies – eg. bowing of the legs Elevate serum alkaline phosphatase Mutation in Xp22.2-22.1 phosphate-regulating endopeptidase gene (PHEX gene) low serum phosphate due to defective resorption of phosphate in proximal renal tubules and inadequate synthesis of 1,25- dihydroxy vitamin D from 25-hydroxyy vitamin D 1/20,000  Inheritance – Single gene disorders Y linked inheritance – Hairy pinna – Transmitted from father to all his sons – Females not affected  Genetic Imprinting In mammals, a small proportion (