Homozygous recessive females may be affected fiv

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Homozygous recessive females- may be affected f.iv. Inheritance may appear to skip generations f.v. Examples: Duchenne muscular dystrophy, classic hemophilia, color blindness g. X-Linked Dominant Disorders g.i. Heterozygous males and females affected g.ii. Reduced penetrance in females g.iii. Example: Fragile X syndrome- most common cause of mental retardation, cognitive disorders, and learning disorders in North America g.iv. 1 in 4000 boys affected
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g.v. 1 in 8000 girls affected g.vi. affected X chromosome appears constricted or broken h. Down Syndrome (trisomy 21)- common chromosomal abnormality h.i. Example of Trisomy - three chromosomes rather than two (21 st pair) h.ii. 47 total chromosomes h.iii. result of non-disjunction or translocation h.iv. risk increases with mother > 35 h.v. S/S: distinctive facial features, small open mouth, protruding tongue, high arched palate, small head, flat face, slanted eyes, brushfield spots on irises, short stature, hypotonic muscles, loose joints, developmental delays, mental retardation i. Chromosomal Disorders i.i. Turner’s Syndrome XO- 45 total chromosomes i.i.1. Affects females- short stature & infertility (lack of ovaries) i.i.2. Aka Monosomy X i.ii. Klinefelter’s Syndrome XXY- extra X chromosome i.ii.1. Affects males- small testes & sperm not produced i.ii.2. Aka Polysomy X j. Multifactorial Disorders j.i. Genetic influences combined with environmental factors j.ii. Examples: cleft palate, congenital hip dislocation, congenital heart disease, type II diabetes mellitus, clubfoot, schizophrenia k. Developmental Disorders k.i. Exposure to alcohol, smoking, radiation, pharmaceuticals, cocaine, maternal infections during child-bearing years k.ii. Exposure to harmful influences in the first 2 weeks of embryonic life usually results in the death of the embryo k.iii. The most critical time is the first 2 months of development when the cells are dividing rapidly and differentiating, organogenesis (formation of organs and systems during embryonic development) is taking place, basic body
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