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Chapter 6 Chromosomes and Cell Reproduction

Chapter 6 Chromosomes and Cell Reproduction. Chromosomes – tightly coiled packages of DNA. Held together by proteins called histones. DNA wraps around the histones then supercoils to form chromosomes. Important Vocabulary.

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Chapter 6 Chromosomes and Cell Reproduction

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  1. Chapter 6Chromosomes andCell Reproduction

  2. Chromosomes – tightly coiled packages of DNA. Held together by proteins called histones. DNA wraps around the histones then supercoils to form chromosomes. Important Vocabulary

  3. Chromatid – two exact copies of a chromosome held together by a centromere. Forms as DNA copies itself before cell division Centromere – holds the chromatids together until they separate Important Vocab

  4. Types of Chromosomes • Sex Chromosomes – are the chromosomes that determine the sex of an organism. • Female: XX • Male: XY • Autosomes– all other chromosomes • Humans: 44 autosomal chromosomes

  5. Chromosomes • Karyotype – is a picture of the chromosomes in a somatic (body) cell. • 22 homologous pairs of autosomes. • 2 sex chromosomes

  6. Chromosomes • Homologous chromosomes – two copies of each autosome (maternal and paternal) • Homologous chromosomes are the same size, shape, and carry genes for the same trait. One comes from mom and one comes from dad.

  7. Chromosomes • Diploid – cells have two sets (maternal and paternal) of chromosomes. • Humans have 46 chromosomes. • Represented by 2n (means a full set of DNA) • Somatic Cells (cells making up the body) • Haploid – cells have one set of chromosomes. • Human haploid cells have 23 chromosomes. • Represented by n (means a half set of DNA) • Gametes (reproductive cells : egg and sperm)

  8. Diploid Cells • Somatic Cells • Cells that make up the body of organisms. • Somatic Cells are produced through Mitosis (cell division results in 2 genetically identical cells).

  9. Interphase The longest stage of a Cell’s life The time spent between divisions Produces all materials required for growth Preparation for division Phases of the Cell Cycle • Interphase: • G1, S, G2 • Mitosis • PMAT • Cytokinesis

  10. Part of one of Interphase is also known as the G1 Phase of the Cell Cycle. This is the Growth Phase where the cell grows and perfoms all of its necessary functions.

  11. The Second part of Interphase is known as the S Phase Synthesis Phase is when DNA replicates copying itself ensuring there will be one full copy of DNA in each daughter cell.

  12. The third part of the Cell Cycle, G2, is a second growth phase where the cell makes the cell is ready for Mitosis. Also a checkpoint to ensure the DNA correctly replicated.

  13. Mitosis: • Cell Division • Mitosis has 4 phases. • Prophase • Metaphase • Anaphase • Telophase

  14. In Prophase the nuclear envelope disintegrates, centrioles move to the poles, spindle fibers develop and begin to move chromosomes toward the center of cell. Spindle Fibers Pair of Centrioles Chromosomes consisting of 2 Sister Chromatids

  15. During Metaphase the Chromosomes line up across center of the cell, also called the equator, or Metaphase plate. Spindle Fibers Equator, or Metaphase Plate Chromosomes

  16. In Anaphase the Chromatids that make up each Chromosome move apart and travel to opposite poles of the cell. Daughter Chromosomes Chromosome

  17. In Telophase an envelope surrounds each set of Chromatids to form new Nucleus and the Cytoplasm starts to divide 2 identical sets of chromosomes Cleavage Furrow

  18. Cytokinesis takes place when the Cytoplasm divides and two cells with identical genetic material are formed Daughter Cells

  19. Let’s Review http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

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