Life Science Chapter 4 Notes Section 4.1 – Cell Division and Mitosis Life Cycle 1) Formation 2) Growth and Development 3) Death Eukaryotic Cell – a cell with a nucleus -­‐ spends most of its life in Interphase – a period of growth and development -­‐ nerve cells and muscle cells are always in Interphase -­‐ copy of hereditary material is made -­‐ After Interphase o Nucleus divides – Mitosis o Cytoplasm divides – Cytokinesis Mitosis – process in which the nucleus divides to form 2 identical cells Stages of Mitosis 1) Prophase 2) Metaphase 3) Anaphase 4) Telophase Chromosome – structure in the nucleus that contains hereditary material Interphase -­‐ Chromosomes duplicate -­‐ Chromosomes become chromatids Prophase -­‐ Chromatids are fully visible -­‐ Nucleolus and the Nuclear Membrane disappear -­‐ Centrioles move to opposite ends of the cell -­‐ Spindle fibers form Metaphase -­‐ Chromatids line up across the center of the cell -­‐ Centromeres attach to spindle fibers Anaphase -­‐ Centromeres divide -­‐ Spindle fibers shorten -­‐ Chromatids separate and move to opposite ends of the cell -­‐ Chromatids are now chromosomes Telophase -­‐ Spindle fibers disappear -­‐ Chromosomes uncoil -­‐ New nucleus forms – 2 new cells Cytokinesis – the division of the cytoplasn -­‐ in plant cells – new cell walls form along the cell plate – new cell membrane develops -­‐ after cytokinesis – the cells goes into interphase again Results of Mitosis 1 cell -­‐-­‐-­‐-­‐à 2 new identical cells with the same # and type of chromosomes 46 = 46 Every body cell = 46 chromosomes or 23 pairs Every sex cell = 23 chromosomes Cell Division Allows for: 1) growth 2) replaces worn out and damaged cells 3) produces new organisms 2 Types of Reproduction 1) Sexual – 2 parents – sperm and egg 2) Asexual – new organism is produced from one organism 3 Types of Asexual Reproduction 1) Fission – cell divides 2) Budding – a bud becomes a new organism 3) Regeneration – regrow damaged or lost parts