5 52213 norm of reaction refers to all the phenotypes

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Unformatted text preview: nmental factors and the child’s genetic makeup. 5 5/22/13 Norm of Reaction Refers to all the phenotypes that could theoretically result from a given genotype , in relation to all the envt in which it could survive and develop PKU   Children with phenylketonuria (PKU) —a disorder that is related to a defective gene on chromosome 12— are unable to metabolize phenylalanine.   With early diagnosis and a properly restricted diet, however, mental retardation resulting from PKU can be avoided. Genetic Transmission of Diseases and Disorders   Over 5,000 human diseases and disorders are presently known to have genetic origins.   Recessive gene: PKU, sickle-cell anemia, Tay-Sachs disease, cystic fibrosis   Single dominant gene: Huntington’s disease, neurofibromatosis   Polygenic inheritance: cancer, heart disease, asthma, psychiatric disorders, behavior disorders 6 5/22/13 Genetic Transmission of Diseases and Disorders   Sex-Linked inheritance: male-pattern baldness, redgreen color blindness, hemophilia, Duchenne muscular distrophy, fragile-X syndrome   Chromosomal anomalies: Down syndrome (trisomy 21), Kleinfelter syndrome (XXY), Turner syndrome (XO) Genetic Transmission of Diseases and Disorders   Regulator gene defects: genetic male with female genitalia   Unidentified genetic basis: autism spectrum disorder (ASD) The Case of MAOA   Young men who had experienced severe maltreatment were in general more likely to en...
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