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Cellular Basis of Genetics

Cellular Basis of Genetics. Medical Genetics. Emphasis. Euchromatin & Heterochromatin Sex Chromatin Lyon hypothesis. Structure of Eukaryote. 1 ． Chromotin & Chromosome. Chromatin : Flemming (1882). Chromosome : Waldeyer (1888). 1 ． Chromotin & Chromosome

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Cellular Basis of Genetics

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  1. Cellular Basis of Genetics Medical Genetics

  2. Emphasis • Euchromatin & Heterochromatin • Sex Chromatin • Lyon hypothesis

  3. Structure of Eukaryote

  4. 1．Chromotin & Chromosome • Chromatin: Flemming (1882) • Chromosome: Waldeyer (1888)

  5. 1．Chromotin & Chromosome 1.1．Euchromatin & Heterochromatin • Euchromatin Chromasomal material that consists of uncoiled dispersed threads during interphase, is genetically active, and stains lightly with basic dyes.

  6. 1．Chromotin & Chromosome 1.1．Euchromatin & Heterochromatin • Heterochromatin Tightly coiled chromosomal material that stains deeply during interphase and is believed to be genetically inactive.

  7. 1．Chromotin & Chromosome 1.1．Euchromatin & Heterochromatin • Heterochromatin • Constitutive heterochromatin • Facultative heterochromatin • Housekeeping gene • Luxury gene

  8. 2．Sex Chromatin • X chromatin • Y chromatin

  9. 2．Sex Chromatin 2.1．X chromatin

  10. 2．Sex Chromatin 2.1．X chromatin A small mass of densely staining chromatin seen during interphase of somatic cells of female mammals. Also called Barr body.

  11. 2．Sex Chromatin 2.1．X chromatin • Lyon hypothesis (1961) • Tri-colored calico cat

  12. 2．Sex Chromatin 2.1．X chromatin • Lyon hypothesis (1961) • Tri-colored calico cat

  13. 2．Sex Chromatin 2.1．X chromatin • Lyon hypothesis • Inactivation of all but one X chromosome • Dosage compensation of X chromosome

  14. 2．Sex Chromatin 2.1．X chromatin • Lyon hypothesis (1961) • Inactivation of all but one X chromosome • Happened at an early stage of embryogenesis • Happened on a random basis and maintained in all descendant cells

  15. 2．Sex Chromatin 2.2．Y chromatin

  16. 3．Sex Determining Mechanism • Chromosomal mechanisms (XY) • Two sex chromosomes of different sizes, X is larger

  17. 3．Sex Determining Mechanism • Chromosomal mechanisms (XY) • Two sex chromosomes of different sizes, X is larger • Females are XX, males are XY • Males determine the sex of the offspring

  18. 3．Sex Determining Mechanism • Chromosomal mechanisms (XY) • Y chromosome TDF : testis-determining factor SRY :sex-determining region of Y chromosome

  19. Emphasis • Euchromatin & Heterochromatin • Sex Chromatin • Lyon hypothesis

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