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Cell Reproduction

Cell Reproduction. Chapter 8. Chromosomes = rod-shaped structures made of DNA and proteins. Histone = protein that helps maintain the shape of chromosomes and aid in the tight packing of DNA. Chromatid = each half of the chromosome, exact copies that have been replicated.

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Cell Reproduction

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  1. Cell Reproduction Chapter 8

  2. Chromosomes = rod-shaped structures made of DNA and proteins Histone = protein that helps maintain the shape of chromosomes and aid in the tight packing of DNA

  3. Chromatid = each half of the chromosome, exact copies that have been replicated Centromere = point where 2 chromatids are attached Chromatin = DNA that is less tightly coiled

  4. Sex chromosomes = determines the sex of an organism; humans have either an X or Y Autosomes = all of the other chromosomes • Every organism is produced by sexual reproduction has 2 copies of each autosome. Homologous chromosome = homologues = same size, shape, and carry genes for same traits

  5. Karotype = photomicrograph of chromosomes = 46 chromosomes exist as 22 homologous pairs of autosomes and 2 sex chromosomes

  6. Genetic Disorder A disease or condition caused by an absent or defective gene or by a chromosomal aberration

  7. Diploid = cells having 2 sets of chromosomes (2n) Haploid = cell having 1 set of chromosomes (1n) = sperm and egg cells • approximately 2 trillion cells (25 million cells per second) are produced by an adult human body everyday

  8. Cell division = process by which cells produce offspring cells Binary Fission = division of a prokaryote cell into 2 offspring cells Asexual reproduction = production of offspring from one parent

  9. Mitosis = cell division in Eukaryote cells; new cells with genetic material that is identical to the first (original cell) - Occurs in organisms undergoing growth, development, repair or asexual reproduction

  10. Cell Cycle • Interphase- time between cell divisions; cell spends most of its time • G1 phase – grow to mature size • S phase – DNA copied (synthesized) • G2 phase – prepares for cell division • Go phase – usually after G1; does not copy DNA, does not divide • Mitosis – nucleus divided • Cytokinesis – cytoplasm divides

  11. Stages of Mitosis

  12. Prophase • shortening & tight coiling of DNA into rod-shaped chromosomes • nucleolus & nuclear envelope breaks down • centrosomes & centrioles appear in animal cells • only centrosomes appear in plant cells • spindle fibers = made of microtubules radiate from centrosomes in preparation of the next phase • mitotic spindle = array of spindle fibers; serves to equally divide chromatids between 2 offspring cells • made up of kinetochore fibers – attached to a disk shaped protein and to one of the chromosomes and polar fibers extend from centrosome to centrosome Kinetos means moving choros means place

  13. Metaphase • kinetochore fibers move chromosomes to center (equator)

  14. Anaphase • chromatids separate at centromere & slowly move toward opposite poles

  15. Telophase • spindle fibers disassemble; chromosomes return to a less tightly coiled chromatin state • nuclear envelope forms around each set of chromosomes; as well as a nucleolus

  16. Cytokinesis (in animals) • begins with the cell membrane pinching inward in the middle between 2 poles (cleavage furrow)

  17. Cytokinesis (in plants) • vesicles from Golgi apparatus join together at the midline to form cell plate • cell wall will eventually form from cell plate

  18. Checkpoints

  19. Crossing over occurs…

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