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Chromosomes

Chromosomes. Each organism has a set # of chromosomes Individuals of the same species have the same # of chromosomes Humans 46. Karyotype. Display of chromosomes All the chromosomes in a cell Arranged by homologous chromosomes. Homologous Chromosomes. One from each parent

caroline-lukas
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Chromosomes

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  1. Chromosomes • Each organism has a set # of chromosomes • Individuals of the same species have the same # of chromosomes • Humans • 46

  2. Karyotype • Display of chromosomes • All the chromosomes in a cell • Arranged by homologous chromosomes

  3. Homologous Chromosomes • One from each parent • There are 23 pairs of homologous chromosomes in each body cell • Have the same sequence of genes on DNA • Control the same traits

  4. More Karyotypes • Normal Male • 22 pairs of body chromosomes • 1 pair of sex chromosomes • 1 X Chromosome • 1Y Chromosome • Normal Female • 22 pairs of body chromosomes • 1 pair of sex chromosomes • 2 X chromosomes

  5. Diploid • Contain 2 of ever chromosome • 46 is the diploid # in humans • 2n • Body Cells

  6. Haploid • Contain 1 of each chromosome • 23 is the haploid # in humans • n • Sex Cells

  7. What does this have to do with anything?

  8. SEX!

  9. Fertilization • The fusion between the sperm and the egg • Creates a Zygote • The first cell of a human • 23 chromosomes from the male and 23 chromosomes from the female (46 total)

  10. How do we make sex cells?

  11. Meiosis (sex cell division)

  12. Let’s Remember… • In Mitosis • Each of the 46 chromosomes double in interphase…92 total chromosomes at the start of prophase • The doubled chromosome look like this…

  13. Lily Anther Cell: Meiosis I (Male) • Interphase I: • Each chromosome has been replicated, exactly as in mitosis. • The cell grows in size.

  14. Prophase I: • The chromosomes shorten and thicken. • The nuclear membrane disappears. • Homologous chromosomes stick to each other and form a Tetrad. • Crossing Over occurs

  15. Metaphase I: • The spindle fibers form. • The centromeres (middle of the tetrad) become attached to the spindle fibers. • The chromosomes line up in the middle of the cell.

  16. Anaphase I: • Double-stranded homologous chromosomes move apart. • The homologous chromosomes that separated are different.

  17. Telophase I: • The chromosomes are at opposite poles. • Cytokinesis separates the two new nuclei into two haploid sister cells.

  18. Lily Anther Cell: Meiosis II • Prophase II: • The chromatids of each chromosome are not wound tightly around each other. • Spindle fibers form again.

  19. Metaphase II: • The chromosomes line up in the middle. • Note that both sister cells are undergoing the process at the same time.

  20. Anaphase II: • The sister centromeres and the sister chromatids separate.

  21. Telophase II: • The chromatids are at opposite poles. • Cytokinesis splits the cells • The result is four separate haploid cells.

  22. Mitosis makes Body Cells • 1 cell division • Produces 2 cells • The same number of chromosomes as the parent cell • 46 Chromosomes in humans • Creates body cells (somatic) • Blood, bone, muscle, nerve, skin… • Takes place all over your body except in your testes or ovaries.

  23. Meiosis makes sex cells • 2 cell divisions • Produces four cells • 1/2 the number of chromosomes as the parent • 23 chromosomes in humans • Creates sex cells (gametes) • Sperm • Egg • Takes place in the testes and ovaries

  24. Errors in Meiosis (Nondisjunction) Ex. Down Syndrome

  25. Errors in Meiosis(Translocation) • Ex. • Leukemia • Carcinomas

  26. Errors in Meiosis(Deletion) • Ex. • Muscular Dystrophy • Cri-Du-Chat Syndrome

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