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Ch.15   genetics ii
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Ch.15 genetics ii

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Transcript

  • 1. Genetics - part two Chapter 15
  • 2. Review• Genes are located on chromosomes• Diploid organisms have two copies of every chromosome• Therefore, two alleles for every gene (except X,Y)
  • 3. Chromosomal basis of Mendel’s Laws• Meiosis• Segregation• Independent assortment
  • 4. Fruit Flies
  • 5. Fruit Flies in Genetics• Small genome – 4 chromosomes• Short generation time• Wild type – most common phenotype – Red eyes• Studies revealed – Sex-linked genes
  • 6. Sex-linked Inheritance
  • 7. Gene Recombination & Crossing Over
  • 8. Constructing a Gene MapThe farther two genes are from each other, thehigher the probability that crossing over will occurbetween them. This can be used to figure outwhere genes are on the chromosome.
  • 9. Some chromosomal systems of sex determination
  • 10. Sex-linked Inheritance
  • 11. Inactivation of the X & Barr Bodies• One X is inactivated during development – becomes Barr body• Same X is not inactivated in all cells• Mosaic in heterozygotes
  • 12. Nondisjuction (during Meiosis)
  • 13. Down Syndrome
  • 14. Genetic disorders caused by abnormal chromosome number (due to nondisjunction)Name Chromosome DescriptionDown syndrome 21 TrisomyEdward’s syndrome 18 TrisomyPatau syndrome 13 TrisomyTurner’s syndrome Single X XOKlinefelter’s syndrome Extra X (in males) XXYXYY syndrome Extra Y (in males) XYYTriple X syndrome Extra X (in females) XXX
  • 15. Alterations of Chromosomes
  • 16. Genomic Imprinting• Some genes behave differently if they come from ova/ sperm• One gene can be “silenced” and the other is expressed• Imprinting is not inherited• Genes are re-imprinted for in the next generation
  • 17. Example: Imprinting• Prader-Willi/ Angelman syndromes• Deletion on chromosome 15• If inherited from father – Prader-Willi syndrome • Mental retardation, obseity, short stature, small hands and feet• If inherited from mother – Angelman syndrome • Spontaneous uncontrollable laughter, jerky movements, motor and mental problems