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Types of Chromosomes and Human Genetic Disorders

Types of Chromosomes and Human Genetic Disorders. Types of Chromosomes Karyotyping Specific disorders. Karyotyping. Taking a photograph of chromosomes (usually from the blood) during mitosis and pairing them (homologous chromosomes paired) to see chromosome abnormalities. Sex Chromosomes.

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Types of Chromosomes and Human Genetic Disorders

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  1. Types of Chromosomes andHuman Genetic Disorders Types of Chromosomes Karyotyping Specific disorders

  2. Karyotyping • Taking a photograph of chromosomes (usually from the blood) during mitosis and pairing them (homologous chromosomes paired) to see chromosome abnormalities.

  3. Sex Chromosomes • X: bigger chromosome than Y • 1200 + genes • Colorblindness, muscular dystrophy, hemophilia • Y: much smaller • 140 genes

  4. Autosomes • 22 pairs (44 total) • Mutations of these chromosomes have a greater affect on a person’s health

  5. Disorders Caused by Individual Genes • Sickle Cell Anemia: caused by a defective allele for a polypeptide in hemoglobin (protein which carries O2) • Makes hemoglobin stick together b/c it’s less soluble and becomes sickle shaped • Clogs capillaries to damage cells, tissue, or organs

  6. Disorders Caused by Individual Genes • Cystic Fibrosis: usually caused by a deletion of 3 bases (removal of phenylalanine from a protein) which causes the protein to be destroyed (recessive) • Leads to tissue malfunctions in digestive system and causes thick, heavy mucus to clog lungs and breathing passageways

  7. Disorders Caused by Individual Genes • Huntington’s Disease: caused by a repeat of CAG (glutamine) more than 40 times • Symptoms include mental deterioration and uncontrollable movements • The greater the # of repeats the earlier the disease appears and it will be more severe

  8. Disorders Caused by Individual Genes • Advantages: • Those heterozygous for sickle cell anemia are highly resistant to malaria and will not get either disease • Proteins produced by CF block the entry of a bacteria that causes typhoid fever—those heterozygous for CF will have an advantage if they live in a city w/ poor sanitation and polluted water and won’t get either ailment

  9. Chromosomal Disorders • Nondisjunction: chromosomes don’t separate during meiosis get abnormal # of chromosomes • Trisomy: 2 copies of autosomes fail to separate so you get 3 copies of a chromosome • Chromosome 21 = Down’s syndrome • XXX = sterile • X chromosome nondisjunction can also cause XO = sterile(Turner’s Syndrome), or XXY = sterile (Klinefelter’s Syndrome)

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