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Transcript
Genetic Disorders Family Pedigrees Definition Presentation of family information in a tree form using standardized symbols. Purpose Determination of how a trait is inherited Determinations Dominant or recessive Autosomal or Sex Linked GENETIC DISORDERS Patterns of Inheritance Autosomal recessive Autosomal dominant X-linked dominant X-linked recessive Y-linked Mitochondrial inheritance Autosomal Recessive Definition Inheritance of two defective alleles is required to express the disorder. Example Cystic Fibrosis Loci 7q31.2-31.3 Defect Nonfunctional chloride channel in mucus, digestive, and sweat glands Result Production of thick mucus and salty sweat Effects Malnutrition, pancreatic cysts, blocked airways Cystic Fibrosis Autosomal Recessive Example Sickle-cell Anemia Loci 11p15.4 Defect Abnormal RBC hemoglobin forming rods Result Fragile, crescent, sickle shaped cells Affects Anemia and clogged capillaries Abnormal HbS molecule. Valine was added instead of Glutamate GLUTAMATE VALINE Sickle Cell Anemia Sickle Cell Anemia AUTOSOMAL RECESSIVE Albinism: absence of pigment in the skin Galactosemia: high liver galactose Phenylketonuria: high phenaylalanine in blood Thalassemia: lack of hemoglobin production Tay-Sachs: lack of gangliosides in nerve cells AUTOSOMAL DOMINANT Definition Inheritance of only one defective allele is required to express the disorder. Example Huntington‘s Disease Loci 4p16.3 Defect Trinucleotide repeats of CAG leading to polyglutamine Mutated huntingtin neural protein leading to toxicity Result Degeneration of nervous system Affects Progressive dementia and death Huntington’s Disease Huntington’s Disease Huntington’s Disease AUTOSOMAL DOMINANT Example Marfan Syndrome Loci 15q21.1 Defect Mutated fibrillin connective tissue protein Result Weakened aortal connective tissue Tall and thin with long arms, legs and fingers Affects Enlarged Aorta subject to rupture. Marfan’s Syndrome Marfan’s Syndrome AUTOSOMAL DOMINANT Familial hypercholesterolemia: high blood cholesterol due to defective liver cell LDL receptors Hypercalcemia: high blood calcium due to faulty parathyroid. Nail-Patella Syndrome: absence of nails and kneecaps. X-Linked Recessive Definition Defect on one X Chromosome . Females are carriers . Males have disorder Example Examples Color blindness Loci Xq28 Defect Mutated opsin proteins in red and/or green cones Result Inability to bind to retinal during activation by light waves Affects Inability to see red or green colors Color Blindness Color Blindness Color Blindness X-Linked Recessive Duchenne Muscular Dystrophy Loci Xp21.1 Defect Mutated dystrophin protein due to deletion of exons Result Lack of attachment of dystrophin to the sarcolemma (plasma membrane) Affects Weakness and wasting of muscle tissue due to tearing of the sarcolemma. Duchenne Muscular Dystrophy Duchenne Muscular Dystrophy Duchenne Muscular Dystrophy Duchenne Muscular Dystrophy X-Linked Dominant Definition Defect on X chromosome . Females have disorder . Males have disorder Examples Coffin-Lowry Syndrome Loci Xp22.2-p22.1 Defect Mutated serine/threonine kinase protein Result Lack of growth factor regulator phosphorylation Affects Craniofacial skeletal abnormalities COFFIN-LOWRY SYNDROME X-Linked Dominant Incontinentia pigmenti Loci Xp11.2 Defect Mutated melanin protein Result Lack of melanin deposition Affect Abnormal skin pigmentation INCONTINENTIA PIGMENTI Y-linked Definition Defect on Y chromosome Examples None Loci Y chromosome Results Loss of male fertility Mitochondrial Inheritance Mitochondria Definition Cytoplasmic organelles that make ATP Genetic makeup Carry 5-10 DNA molecules of 37 genes Inheritance From mothers to offspring through ovum Results Impaired energy conversion Affects Nerves, muscles, liver, and kidneys Examples Kearns-Sayre syndrome: short stature, retinal degeneration MERRF Syndrome: lack of energy transfer VARTIATIONS IN CHROMOSOMAL NUMBER Types Euploid Normal chromosome number Polyploid Extra set(s) of haploid chromosomes Aneuploid Gain or loss of a single chromosome POLYPLOID ANEUPLOID VARTIATIONS IN CHROMOSOMAL NUMBER Turner Syndrome (45,XO) Definition Inheritance of one X chromosome without a partner X or Y chromosome. Etiology Paternal nondisjunction (75%) Physical Features Short and wide-chested Small jaw Webbed neck Ovarian failure w/ lack of puberty Underdeveloped sex characteristics TURNER’S SYNDROME VARTIATIONS IN CHROMOSOMAL NUMBER Klinefelter Syndrome (47, XXY) Definition Inheritance of two X chromosomes as well as one Y chromosome. Etiology Maternal nondisjunction (60%) Physical Features Male with poor sex development Breast development Very low fertility Degree of subnormal intelligence KLINEFELTER SYNDROME VARTIATIONS IN CHROMOSOMAL NUMBER Jacobs Syndrome (47,XYY) Definition Inheritance of two Y chromosomes as well as one X. Etiology Paternal nondisjunction during meiosis II Physical Features Above average height Degree of subnormal intelligence JACOB’S SYNDROME VARTIATIONS IN CHROMOSOMAL NUMBER Poly-X (Meta) Females (XXX, XXXX) Definition More than two X chromosomes Etiology Maternal nondisjunction Physical Features Long legs and slender torsos Normal sexual characteristics Meta Female karyotype Trisomy 23 Hermaphroditism Definition Individuals with both ovarian and testicular tissue. Etiology Mosaicism Cells of two kinds (XX & XY) Sex Chromosome Crossing Over Exchange of testis determining factor (TDF) from the Y chromosome MOSAICISM MOSAIC EXPRESSION TESTES DETERMINING FACTOR Hermaphroditism Physical Features Mosaicism Male features dominate Sex Chromosome Crossing Over Female: XY without TDF Male: XX with TDF Androgen Insensitivity Definition XY individuals develop as phenotypic females Etiology Androgen receptor gene mutation Loci Xq11-13 Results Lack of interaction between cell and testosterone Physical Features Lack of normal female reproductive tract Well-developed breasts Little pubic hair ANDROGEN INSENSITIVITY