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Cell Reproduction

This overview explores the structure and function of chromosomes in cell reproduction, primarily focusing on DNA, which stores genetic information through genes composed of four bases: adenine, thymine, guanine, and cytosine. It distinguishes between sex chromosomes (XY for males, XX for females) and autosomes. The text reviews chromosome duplication, a karyotype example, diploid versus haploid cells, and the processes of mitosis and meiosis, detailing each stage of cell division. Finally, it contrasts sexual and asexual reproduction, highlighting key differences in genetic variation.

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Cell Reproduction

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Presentation Transcript

  1. Cell Reproduction

  2. Chromosomes: made of DNA

  3. DNA: stores all genetic information -genes:a hereditary unit of DNA -4 bases: -Adenine -Thymine -Guanine -cytosine

  4. DNA in the Cell • Chromosome • Supercoil • Subcoil • One coil • DNA with histine protein • DNA

  5. Chromosome Anatomy

  6. Chromosome Types • Sex Chromosomes: determines the sex of an organism -XY: male -XX: female • Autosomes: All other chromosomes of an organism

  7. Chromosome Duplication

  8. Homologous Chromosomes: two copies of each autosome – same size, shape, and genes

  9. Karyotype: photomicrograph of chromosomes Humans have 22 pairs of autosomes and 1 pair of sex chromosomes

  10. Diploid Cells (2n): cells with both sets of chromosomes (both homologous pairs) 46 chromosomes/23 pairs in humans

  11. Haploid cells (1n): cells with one set of chromosomes

  12. “C” words of Cytology 1. Chromosome: condensed genetic material • Chromatid: one of two identical copies of DNA • Centromere: region that joins the chromatids

  13. “C” words of Cytology • Centrioles: cylindrical structures that assist in cell division • Centrosome: dark regions in the cytoplasm that create spindle fibers

  14. Cell Division: all cells come from pre-existing cells

  15. 2 Types of Division

  16. 1. Mitosis: cell division which produces 2 diploid, identical cells

  17. 2. Meiosis: cell division which produces 4 haploid cells

  18. Cell Life Cycle Interphase: G1, S, and G2 G = growth S = Synthesis M phase: mitosis – nuclear division Cytokinesis: cytoplasm division

  19. Interphase 1. Interphase: DNA not visible -nucleus still intact

  20. Phases of Mitosis • Prophase: chromosomes become visible -nucleus disintegrates

  21. Phases of Mitosis • Metaphase: chromosomes connect at the centromere to spindle fibers -line up at the equatorial plate

  22. Phases of Mitosis • Anaphase: spindle fibers recede -pull chromosomes apart -chromosomes retreat to opposite ends

  23. Phases of Mitosis • Telophase: nucleus reforms Cytokinesis splitting the cell -2 daughter cells are formed

  24. Meiosis: cell division which produces 4 haploid cells

  25. Haploid: a cell with half the number of chromosomes (1n)

  26. Fertilization: the fusion of two gametes (sperm/eggs)

  27. Review terms:

  28. Karyotype

  29. Homologous Chromosomes: identical chromosomes – one from each parent

  30. Chromatid: one of two identical copies of the same DNA

  31. Mitosis vs. Meiosis Mitosis Meiosis -produces four offspring cells of 1n -two cell division cycles (meiosis I & 2) -produces gametes -chromosomes cross over -Produces two offspring cells of 2n -One cell division cycle -produces body cells -no chromosomes cross over

  32. 8 Stages of Meiosis Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II Meiosis I Meiosis II

  33. Prophase I -Chromatids form -Homologous chromatids pair up to form tetrads

  34. Metaphase I -tetrads line up at equatorial plate -Crossing over: breaking off of arms of chromatids and switching places on another homologous chromosome

  35. Anaphase I -tetrads are pulled apart

  36. Telophase I -cytokinesis occurs

  37. Prophase II

  38. Metphase II

  39. Anaphase II

  40. Telophase II

  41. Spermatogenesis: meiosis that produces sperm Produces 4 fertile cells; in humans @ 400 billion

  42. Oogenesis: meiosis that produces egg cells Produces 1 fertile cell; about 400 in a lifetime

  43. Types of Reproduction • Sexual reproduction: offspring are the result of combination of parental genetics • Asexual reproduction: no exchange of genetic information – genetically identical to parent

  44. Nature protects the female

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