Multifactorial disorders large of disorders are of

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Multifactorial disorders- large # of disorders are of this type b.iv.1. Often have pattern of familial inheritance b.iv.2. Environmental component b.iv.3. Affect approximately 10% of the population b.iv.4. May be polygenic - caused by multiple genes b.v. Other congenital or developmental disorders b.v.1. Result from premature birth b.v.2. Difficult labor and delivery b.v.3. Example: cerebral palsy c. Single Gene Disorders- classified by inheritance patterns (recessive, dominant, x- linked recessive) c.i. Single gene controls a specific function (color blindness) c.ii. More than 6000 known, 1 in 200 births c.iii. May have systemic effects (cystic fibrosis or marfan syndrome)
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d. Autosomal Recessive Disorders d.i. Both parents must pass on allele for disorder d.ii. Homozygous - having 2 identical alleles at corresponding points on a chromosome pair (rr or RR) d.iii. Heterozygous - having 2 different alleles at corresponding points on a chromosome pair (Rr) d.iv. Male and female affected equally d.v. Homozygous recessive child has disorder d.vi. Incomplete dominance - heterozygotes may display some clinical signs whereas homozygotes show full range of expression (sickle cell) d.vii. Examples: cystic fibrosis, PKU, sickle cell anemia, Tay-Sachs disorder RR unaffected Rr carrier Rr carrier rr affected e. Autosomal Dominant Disorders e.i. Inheritance of one allele causes disorder- only one parent needs to carry allele e.ii. No carriers= unaffected persons don’t transmit it e.iii. Some conditions become evident later in life e.iii.1. Allele for disorder passed on before diagnosis of disease in parent e.iii.2. Termed “delayed lethal” genotype e.iv. Examples: adult polycystic kidney disease, Huntingtons disease, familial hypercholesterolemia, Marfan syndrome f. X-Linked Recessive Disorder- allele carried on X chromosome, not on Y f.i. Manifested in heterozygous males lacking the matching unaffected gene on the Y chromosome f.ii. Heterozygous females- carriers f.iii.
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