asexual reproduction & mitosis notes
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Asexual Reproduction & MitosisNotes
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?
1. 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 organismsExample: 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 plantsNew 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: – 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
(Figure 12.6 in your book)
Centrosomes
chromatin -uncondensedchromosomes
G2 of Interphase Prophase
-sister chromatids/chromosomes-nuclear envelope breaks down
-mitotic spindle
Metaphase
-metaphase plate
AnaphaseTelophase&
Cytokinesis
-chromosomes pull apart
-cleavage furrow
-nuclear envelope reforms
Chromosomes move to middle
Mitosis
Prophase
Metaphase
Anaphase
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)
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