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Chromosome Theory of Inheritance

Chromosome Theory of Inheritance. Genes occupy a specific place on a chromosome During meiosis, chromosomes undergo: Segregation Independent assortment. Discovery of theory. Thomas Morgan Fruit flies Wings (W=normal, w=small) Body color (G=gray, g=black) Cross GgWw x ggww

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Chromosome Theory of Inheritance

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  1. Chromosome Theory of Inheritance • Genes occupy a specific place on a chromosome • During meiosis, chromosomes undergo: • Segregation • Independent assortment

  2. Discovery of theory • Thomas Morgan • Fruit flies • Wings (W=normal, w=small) • Body color (G=gray, g=black) • Cross GgWw x ggww • Expect to get • ¼ GgWw ¼ ggWw, ¼ Ggww, ¼ ggww,

  3. Instead Morgan found……. • A majority were GgWw or ggww • He discovered that genes were linked on the same chromosome, therefore do not undergo independent assortment

  4. Crossing over creates variety • When homologous chromosomes line up, parts can overlap break apart and swap pieces of the chromosome • Creates recombinants=new combo of genes • Further apart 2 genes are=more likely to cross over

  5. Karyotype-picture taken of the chromosomes during meiosis

  6. Chromosome pairs arranged from longest to shortest

  7. 2 types of Chromosomes • Autosomes-22 pairs • Sex chromosomes-1 pair • XX female • XY male

  8. Chromosomal Disorders • Occur when chromosomes don’t separate properly during meiosis

  9. Nondisjuction

  10. Down’s Syndrome3 Chromosome #21

  11. Common symptoms of Down’s • Flat facial features, • Upward slanted eyes • Short neck • Large and protruding tongue • infertile • life span =about 55 years.

  12. RELATIONSHIP OF DOWN's SYNDROME INCIDENCE TO MOTHERS' AGE Mothers Age (Years) Incidence of Down's Syndrome Under 30 Less than 1 in 1,000 30 1 in 900 35 1 in 400 36 1 in 300 37 1 in 250 38 1 in 180 39 1 in 135 40 1 in 105 42 1 in 60 44 1 in 35 46 1 in 20 48 1 in 16 49 1 in 12 Source: Hook, E.G., Lindsjo, A. Down Syndrome in Live Births by Single Year Maternal Age.

  13. Turner’s Syndrome-45X

  14. Symptoms of Turner’s • Short stature • Webbed neck • Broad, flat chest • Small breasts • Infertility • No menstruation

  15. Klinefelter’s Syndrome- 47XXY

  16. Symptoms of Klinefelter’s • Small penis /testicles • Enlarged breast tissue • Little to no facial/body hair • Quite tall • infertility

  17. 47XYY syndrome • Extra Y • May show increased activity, aggressiveness • Delayed mental maturity • Learning disabilities • Increased height • Are fertile

  18. Pedigree-chart used to show a family history of a trait

  19. Sex-linked traits • Those genes found on the sex chromosomes • Usually on the X • Usually passed from mother to children (boys) • Examples • Color-blindness • Muscular Dystrophy • Hemophilia

  20. Color-blindness X Y C=normal vision c=color-blind X X

  21. Hemophilia H=normal h=hemophilia X Y X Cross a man with hemophilia with a carrier female X

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