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Chromosomes & Inheritance

Chromosomes & Inheritance. Human Genetic Disorders and Diseases. Sex Chromosomes -chromosome pair #23. Autosomes -chromosome pairs 1-22. Sex Linkage. Genes found on the X chromosome are X- linked. Genes found on the Y chromosome are Y-linked.

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Chromosomes & Inheritance

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  1. Chromosomes & Inheritance Human Genetic Disorders and Diseases

  2. Sex Chromosomes -chromosome pair #23 Autosomes -chromosome pairs 1-22

  3. Sex Linkage Genes found on the X chromosome are X- linked. Genes found on the Y chromosome are Y-linked. Presence of a gene on a sex chromosome is called sex linked…meaning one sex may have a higher chance of getting a disease over the other sex. Genes found on the same chromosome are inherited together. (Thomas Morgan, early 1900’s)

  4. Locating Genes…Human Genome Project All genes are mapped out on our 23 pairs of chromosomes. Example: hemophilia

  5. What Causes Genetic Disorders? Mutations: can involve a change in a chromosome or sequence of DNA. -Germ cell mutations: occur in an organisms sex cells (gametes). These are passed onto offspring. -Somatic mutations: occur in the organisms body cells. These are not passed on to offspring. -Lethal mutations: cause death in embryo before birth.

  6. Chromosome Mutations Three types of chromosome mutations: 1. Deletion 2. Inversion (same chromosome) 3. Translocation -Mutations can also lead to nondisjunction- failure of chromosomes to separate. Results in an abnormal number of chromosomes in a cell. Example: Trisomy 21 (Down’s Syndrome)

  7. Chromosomal Mutations

  8. Klinefelter’s Syndrome: males with feminine characteristics. Turner’s Syndrome: females with many physical developmental and mental issues.

  9. Gene (DNA) Mutations Point Mutation- substitution, addition, or removal of a single nucleotide. Point mutations lead to frameshift mutations, different amino acids being linked together. -Sickle-cell anemia Normal sequence is CTT Mutated sequence is CAT Instead of Glutamic Acid…you get Valine!

  10. Gene Mutation

  11. Human Genetics -Scientist study human inheritance by studying a pedigree. They look for patterns of inheritance and carriers.

  12. Queen Victoria Family Pedigree

  13. Genetic Traits and Disorders: Inheritance Patterns Polygenic: trait that is controlled by two or more genes. Exp. skin color, eye color, human height. Many polygenic traits also are controlled by environmental factors. (Complex Characteristics) Multiple-Allele: traits controlled by three or more alleles. Exp. ABO blood groups. The three alleles are IA IB & i. Type A = IAIA or IA i Type B = IB IBor IB i Type AB = IAIB Type O = i i

  14. Incomplete Dominance: not completely dominant; heterozygous condition is a blend of the characteristics. Exp. blood cholesterol levels in humans. Codominance: Dominance is shared. Exp. Roan or speckled coloration patterns. Sex-Linked Traits: X-Linked examples are colorblindness and hemophilia. Y-Linked are more rare…only occur in males. Exp. Hemophilia: XhYXhXh Normal: XHY XHXH What about XHXh ?

  15. Sex-Influenced Traits: caused by the presence of male or female hormones. Exp.- baldness. Autosomal Recessive: Two recessive alleles. Exp. Cystic Fibrosis, Sickle Cell Anemia, Tay-Sachs Autosomal Dominant: Two dominant alleles. Exp. Breast cancer (not all types), MarfanSyndrome Single-Allele: traits controlled by a single allele. Exp. Huntington’s disease (autosomal dominant).

  16. Blood Types & Frequency: Type O - 44% Type A - 42% Type B - 10% Type AB - 4% -RH Factor (+ or -) -Medical condition: ErythroblastosisFetalis

  17. Detection of Human Genetic Disorders: -Genetic screening (karyotypes) -Genetic counseling -amniocentesis -chorionic villi sampling -PKU tests right after birth (special diet for infants)

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