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Genetic Disorders

Genetic Disorders. A disease caused by a different form of a gene called a variation , or an alteration of a gene called a mutation. How genetic disorders occur. Monogenetic disorder – mutation of a single gene Is inherited Examples sickle cell anemia.

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Genetic Disorders

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  1. Genetic Disorders A disease caused by a different form of a gene called a variation, or an alteration of a gene called a mutation.

  2. How genetic disorders occur • Monogenetic disorder – mutation of a single gene • Is inherited • Examples sickle cell anemia

  3. Multifactorial inheritance disorders • Caused by a combination of small inherited variations in genes, often acting together with environmental factors. • Examples - Heart disease, diabetes, and most cancers

  4. Chromosomal disorders • Alteration of chromosome number • Example – Downs Syndrome – extra chromosome

  5. Alteration of chromosome number • Diagnosed with Karyotype • fetal cells must be harvested and cultured in vitro. • The chromosomes are removed and arranged in pairs and photographed. • Abnormalities in chromosome number, shape, or size can be detected this way.

  6. Causes • Nondisjunction • one gamete receives two of the same type of chromosome, and another gamete receives no copy. • Problems with the meiotic spindle cause errors in daughter cells • Tetrad chromosomes do not separate properly during meiosis I • sister chromatids may fail to separate during meiosis II

  7. Offspring from nondisjunction • Have abnormal chromosome number - aneuploidy. • Trisomic cells have three copies of a particular chromosome type and have 2n + 1 total chromosomes. •  Monosomic cells have only one copy of a particular chromosome type and have 2n - 1 chromosomes.

  8. Examples of aneupoidyTrisomy • Downs syndrome –trisomy 21 (3 copies of chromosome 13) • Patu syndrome – trisomy 13 • Very short life span – less than 1 year • Edwards syndrome – trisomy 1 • Life span less than 10 weeks • Kleinfelters syndrome XXY • Normal intelligence – abnormal sex organs

  9. Monosomy • XYY – males taller than normal • XXX – females indistinguishable from XX females • Turners syndrome – monosomy X • Only know viable monosomy in humans

  10. Task • Karyotyping activity at Bio Project • http://www.biology.arizona.edu/human_bio/activities/karyotyping/Karyotyping.html • Evaluate 3 patients' case histories, • Complete their karyotypes, and • Diagnose any missing or extra chromosomes • Do an internet search to explain your diagnoses.

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