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Mutations

Mutations. Chromosomal Mutations (errors of cell division) Point Mutations (errors of DNA replication). Part 1: Chromosomal Mutations. Errors of Cell Division. Karyotypes. Photograph of chromosomes, arranged by homologous pairs First 22 pairs (in humans) are “autosomes”.

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Mutations

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  1. Mutations Chromosomal Mutations (errors of cell division) Point Mutations (errors of DNA replication)

  2. Part 1: Chromosomal Mutations Errors of Cell Division

  3. Karyotypes • Photograph of chromosomes, arranged by homologous pairs • First 22 pairs (in humans) are “autosomes”. • Last pair are sex chromosomes • XX = female, XY = male

  4. Aneuoploidy • Cells that have an abnormal number of chromosomes are aneuploid. Down Syndrome Female 47 XX +21 Normal Female 46 XX

  5. Some Common Aneuoploidies X X X Turner’s Syndrome 45 X Triple X Syndrome 47 XXX

  6. More Common Aneuoploidies X Y Y X X Y Klinefelter’s Syndrome 47 XXY XYY Syndrome 47 XYY

  7. Anuoploidy Results from Nondisjunction of Sister Chromatids, During Mitosis or Meiosis

  8. Errors Occur in Mitosis and Meiosis Errors of Mitosis Errors of Meiosis Errors of meiosis are passed to every cell of an offspring Called “germ line mutations” • Errors of mitosis are confined to daughter cells (not hereditary) • Called “somatic mutations”

  9. Nondisjunction • Nondisjunction is the failure of chromosomes to separate during cell division, leading to asymetrical distribution between daughter cells.

  10. Nondisjunction (continued) • Most chromosomal mutations of mitosis or meiosis are due to nondisjunction of sister chromatids, during anaphase (anaphase II in meiosis) • Additionally, in meiosis I, nondisjunction may occur between homologous chromosomes

  11. Somatic Mutation • Somatic mutations occur in body (somatic) cells and affect only the daughter cells of the affected cell. • Moles and some cancers are the results of somatic mutations.

  12. Nondisjunction can occur when spindle fibers from one centriole attach to both sister chromatids (mitosis & meiosis II) or both homologous chromosomes (meiosis I) Spindle fibers from one centriole attaching to both sister chromatids

  13. Homologous chromosomes Sister chromatids Mitosis:Metaphase

  14. Chromosomes align across the “equator” of the cell, one sister chromatid on each side.

  15. Mitosis:Anaphase Nondisjunction of sister chromatids

  16. Mitosis:Telophase & Cytokinesis Nuclei form

  17. Interphase Daughter cells are aneuoploid Karyotype: 2n + 1 (trisomy) Karyotype: 2n – 1 (monosomy)

  18. Germ Line Mutation • Errors that occur in gamete production affect offspring.

  19. Homologous chromosomes line up across the middle Sister chromatids Meiosis I:Metaphase

  20. Meiosis I:Anaphase Nondisjunction causes both homo chromo’s to be in one cell

  21. Meiosis I:Telophase

  22. End of Meiosis I • 2 aneuoploid daughter cells formed

  23. Meiosis II: Prophase

  24. Meiosis II: Metaphase Chromosomes line up at “equator” of cell.

  25. Meiosis II: Anaphase Sister chromatids separate to opposite sides of cell.

  26. Meiosis II: Telophase 4 aneuoploid haploid cells form (sperm or eggs)

  27. Meiosis II: Telophase Karyotype N + 1 Karyotype N - 1

  28. Part 2: Point Mutations Errors of DNA Replication

  29. Single Nucleotide Substitution

  30. Deletion

  31. The fat cat ate the big rat. The frt cat ate the big rat. The ftc ata tet heb igr at…..

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