3 - Cell Cycle MITOSIS.pdf

CELLULAR DIVISION 1 Cell Division: Let’s Review… ✔ All cells are derived from pre-existing cells ✔ New cells are produced for growth and to replace damaged or old cells ✔ Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals)...

CELLULAR DIVISION 1 Cell Division: Let’s Review… ✔ All cells are derived from pre-existing cells ✔ New cells are produced for growth and to replace damaged or old cells ✔ Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals) 2 Recall Chromosomes in Dividing Cells Called Sister Chromatids ✔ Duplicated chromosomes are called chromatids & are held together by the centromere 3 Cell Reproduction 4  Types of Cell Reproduction ✔Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells ✔Mitosis & binary fission are examples of asexual reproduction ✔Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells ✔Meiosis is an example 5 THE CELL CYCLE 6 Five Phases of the Cell Cycle ✔ Interphase ✔ G1 - primary growth phase ✔ S – synthesis; DNA replicated ✔ G2 - secondary growth phase ✔ M - mitosis ✔ C - cytokinesis 7 Interphase - G1 Stage ✔ 1st growth stage after cell division ✔ Cells mature by making more cytoplasm & organelles ✔ Cell carries on its normal metabolic activities 8  Interphase – S Stage ✔ Synthesis stage ✔ DNA is copied or replicated Two identical copies of DNA Original DNA 9 Interphase – G2 Stage ✔ 2nd Growth Stage ✔ Occurs after DNA has been copied ✔ All cell structures needed for division are made (e.g. centrioles) ✔ Both organelles & proteins are synthesized 10  Cell Cycle DNA Copied Cells prepare for Cells Division Mature Daughter Cells Cell Divides into Identical cells 11 Mitosis 12  Mitosis ✔ Division of the nucleus ✔ Also called karyokinesis ✔ Only occurs in eukaryotes ✔ Has four stages ✔ Doesn’t occur in some cells such as brain cells 13  Four Mitotic Stages ✔ Prophase ✔ Metaphase ✔ Anaphase ✔ Telophase 14  Early Prophase ✔ Chromatin in nucleus condenses to form visible chromosomes ✔ Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal) Nucleolus Cytoplasm Nuclear Membrane Chromosomes 15  Late Prophase ✔ Nuclear membrane & nucleolus are broken down ✔ Chromosomes continue condensing & are clearly visible ✔ Spindle fibers called kinetochores attach to the centromere of each chromosome ✔ Spindle finishes forming between the poles of the cell 16  Late Prophase Chromosomes Nucleus & Nucleolus have disintegrated 17  Spindle Fiber attached to Chromosome Kinetochore Fiber Chromosome 18  Metaphase ✔ Chromosomes, attached to the kinetochore fibers, move to the center of the cell ✔ Chromosomes are now lined up at the equator Equator of Cell Pole of the Cell 19  Metaphase Asters at the poles Spindle Chromosomes Fibers lined at the Equator 20  Anaphase ✔ Occurs rapidly ✔ Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers 21  Anaphase Sister Chromatids being separated 22  Telophase ✔ Sister chromatids at opposite poles ✔ Spindle disassembles ✔ Nuclear envelope forms around each set of sister chromatids ✔ Nucleolus reappears ✔ CYTOKINESIS occurs ✔ Chromosomes reappear as chromatin 23 Comparison of Anaphase & Telophase 24  Cytokinesis ✔ Means division of the cytoplasm ✔ Division of cell into two, identical halves called daughter cells ✔ In plant cells, cell plate forms at the equator to divide cell ✔ In animal cells, cleavage furrow forms to split cell 25  Cytokinesis Cleavage Cell plate in furrow in animal plant cell cell 26 Mitotic Stages 27  Daughter Cells of Mitosis ✔ Have the same number of chromosomes as each other and as the parent cell from which they were formed ✔ Identical to each other, but smaller than parent cell ✔ Must grow in size to become mature cells (G1 of Interphase) 28  Identical Daughter Cells What is the 2n or diploid number ? 2 Chromosome number the same, but cells smaller than parent cell 29 Checkpoints in the Cell Cycle During the cell cycle, the cell is controlled at checkpoints where it is monitored. Messages are sent to the cell’s nucleus to “divide, or not to divide” Checkpoints in the cell G1 gap phase 1 – does the cell have enough energy? Is it large enough? S synthesis phase – DNA replication: Cyclins/cyclin dependent kinase (CDKs) signal the division G2 gap phase 2 – cell size/energy reserves are assessed. More importantly: have ALL chromosomes been replicated without mistakes/damaged? M checkpoint (metaphase): aka spindle checkpoint – are the sister chromatids attached correctly? Review of Mitosis 32 Mitosis in Onion Root Tips Do you see any stages of mitosis? 33 Test Yourself over Mitosis 34 Mitosis Quiz 35 Mitosis Quiz 36 Locate the Four Mitotic Stages in Plants Anaphas e Telophase Metaphase Prophase 37