Asexual Reproduction & Mitosis

Asexual Reproduction Definition: one parent produces genetically identical offspring Advantages: Can produce offspring w/o a mate Many offspring in short time Disadvantages: No variation in offspring No adaptation to new/changing environments

Asexual Reproduction What kinds/types of reproduction are asexual? Budding - a new individual grows on a ‘parent’ Example: hydra, yeast

Asexual Reproduction What kinds of reproduction are asexual? 2. Binary Fission - a ‘parent individual’ splits into two independent organisms Example: bacteria

Asexual Reproduction What kinds of reproduction are asexual? 3. Regeneration - fragments of the ‘parent’ can grow into new organisms Example: starfish, planarian

Asexual Reproduction What kinds of reproduction are asexual? 4. Parthenogenesis - production of offspring from unfertilized eggs

Asexual Reproduction What kinds of reproduction are asexual? 5. Vegetative reproduction - occurs in plants New plants rise w/o the production of seeds or spores

Mitosis Makes two cells that are genetically identical to each other Purpose? – growth and repair

Chromosomes -Passed on from one generation to the next -Genetic material composed of genes which are made up of DNA Only visible during cell division Found in the nucleus Condensed DNA

How DNA forms chromosomes

Chromatin Chromatin – uncondensed DNA; appears very “stringy” Form of DNA between cell divisions

Parts of a Chromosome Sister chromatids: identical copies of a chromosome Made during the S phase of the cell cycle Centromere: holds two sister chromatids together

The Cell Cycle

The Cell Cycle Interphase: Mitotic Phase: G1 phase: cell growth S phase: DNA is replicated/copied G2 phase: more cell growth Mitotic Phase: Mitosis/Cell Division Cytokinesis (division of cytoplasm)

Mitosis Prophase Anaphase Metaphase Telophase

Prophase of Mitosis Chromatin coils up into visible chromosomes Centrioles migrate to opposite ends Nuclear envelope and nucleolus break down Centromere of chromosome starts to attach to spindle fibers

Metaphase of Mitosis Chromosomes line up in the middle of the cell

Anaphase of Mitosis Spindle fibers contract (shorten) Chromosomes are pulled apart Sister chromatids move to opposite poles

Telophase of Mitosis Chromosomes gather at opposite poles Nuclear envelope starts to reform

Cytokinesis Division of the cytoplasm Plant Cells: cell plate is formed → cell wall Animal Cells: cleavage furrow formed

Summary of Mitosis Start with 1 parent cell and ends with 2 daughter cells 2 daughter cells are formed that are genetically identical to the parent cell Occurs in somatic cells (aka, body cells) Functions in growth and repair of cells

Virtual Animation of Mitosis Check out this site: Virtual Mitosis Animation

Cell Cycle Regulation Cyclin – a group of proteins that regulates the timing of the cell cycle Controls when cells go from G1 to S phase Controls when cells go from S to G2 phase Controls when cells go from G2 to M phase

Uncontrolled Cell Growth Cancer – abnormally rapid cell division Cells of the tumor may break lose and spread or metastasize through the body May be caused by radiation, pollution, bad luck, viral exposure Many cancer cells have a mutation/defect in gene p53 (gene that normally tells the cell to wait until all chromosomes have been replicated before proceeding to mitosis)