AP Biology Biology is the only subject in which multiplication is the same thing as division…

AP Biology The Cell Cycle: Cell Growth, Cell Division, Mitosis & Meiosis

AP Biology Where it all began…  You started as a cell smaller than a period at the end of a sentence….

AP Biology Getting from there to here…  Cell division  continuity of life = reproduction of cells  reproduction  unicellular organisms  growth  repair & renew  Cell cycle  life of a cell from origin to division into 2 new daughter cells

AP Biology Getting the right stuff  What is passed to daughter cells?  exact copy of genetic material = DNA  this division step = mitosis  assortment of organelles & cytoplasm  this division step = cytokinesis

AP Biology Copying DNA  Dividing cell duplicates DNA  separates each copy to opposite ends of cell  splits into 2 daughter cells  human cell duplicates ~3 meters DNA  separates 2 copies so each daughter cell has complete identical copy

AP Biology Cell cycle  Cell has a “life cycle” cell is formed from a mitotic division cell grows & matures to divide again cell grows & matures to never divide again G 1, S, G 2, MG0G0 epithelial cells, blood cells, stem cells brain nerve cells liver cells

AP Biology Cell Division cycle  Phases of a dividing cell’s life  interphase  cell grows  replicates chromosomes  produces new organelles  mitotic phase  cell separates & divides chromosomes  mitosis  cell divides cytoplasm & organelles  cytokinesis

AP Biology Interphase  90% of cell life cycle  Characteristics  nucleus well-defined  DNA loosely packed in long chromatin fibers

AP Biology Mitosis  copying cell’s DNA & dividing it between 2 daughter nuclei  Mitosis is divided into 4 phases  prophase  metaphase  anaphase  telophase

AP Biology Prophase  DNA condenses  visible as chromosomes  Centrioles move to opposite poles of cell  Spindle forms  Nucleolus disappears  Nuclear membrane breaks down

AP Biology Metaphase  Chromosomes align along the middle of cell  meta = middle  helps to ensure chromosomes separate properly  so each new nucleus receives only 1 copy of each chromosome

AP Biology Anaphase  Sister chromatids separate  move to opposite poles  Poles move farther apart

AP Biology Telophase  Chromosomes arrive at opposite poles  nuclei form  nucleoli form  chromosomes disperse  Cytokinesis begins  cell division

AP Biology Cytokinesis  Animals  Cleavage occurs  The cytoplasm is beginning to divide in half

AP Biology Cytokinesis in Animals

AP Biology Mitosis in whitefish blastula

AP Biology onion root tip

AP Biology Methods of Asexual Reproduction  Binary Fission  Budding  Sporulation  Vegetative Propagation

AP Biology Asexual reproduction  Bacteria  Divide by binary fission  equal division of both the cytoplasm and nucleus to form two identical organisms  Single-celled eukaryotes reproduce asexually  yeast  Amoeba  Simple multicellular eukaryotes reproduce asexually  Hydra  budding

AP Biology Sporulation  spore formation  is reproduction involving specialized single cells coming from one parent  the diagram of mold spores being formed below is an example of this

AP Biology Vegetative Propagation  Production of a new plant from a portion of another plant, such as a stem or branch.

AP Biology How about the rest of us?  What if a complex multicellular organism (like us) wants to reproduce?  joining of egg + sperm  Do we make egg & sperm by mitosis? eggspermzygote

AP Biology How do we make sperm & eggs?  reduce 46 chromosomes  23 chromosomes  half the number of chromosomes egg sperm 46 meiosis 46 fertilization 23

AP Biology Meiosis = reduction division  Meiosis  special cell division in sexually reproducing organisms  reduce 2n  1n  diploid  haploid  half  makes gametes  sperm, eggs

AP Biology nd division of meiosis separates sister chromatids 1st division of meiosis separates homologous pairs Double division of meiosis DNA replication

AP Biology Mitosis vs. Meiosis  Mitosis  1 division  daughter cells genetically identical to parent cell  produces 2 cells  2n  2n  produces cells for growth & repair  no crossing over  Meiosis  2 divisions  daughter cells genetically different from parent  produces 4 cells  2n  1n  produces gametes  crossing over

AP Biology Crossing over  During Prophase 1  homologous pairs swap pieces of chromosome  sister chromatids intertwine  crossing over tetrad