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Mitosis

Mitosis. [Remember: Mitosis happens in my toesies]. Purposes of cell division. Increase the number of cells for growth and repair of worn out tissues (mitosis) Transmit genetic information (DNA) to other cells

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Mitosis

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  1. Mitosis [Remember: Mitosis happens in my toesies]

  2. Purposes of cell division • Increase the number of cells for growth and repair of worn out tissues (mitosis) • Transmit genetic information (DNA) to other cells • We will study transmitting DNA to other generations later: Reproduction and heredity

  3. Mitosis: One cell becomes two • Each daughter cell gets exactly the same DNA. • Mitosis goes on in all parts of a Eukaryotes body. • Prokaryotes use a different method — “Binary fission” to divide.

  4. Chromosomes are coiled strands of instructions (DNA) This is a chromosome in the “mother” cell This is also called a chromosome, but it has doubled itself so that there is one copy for each “daughter” cell. This is an actual image of a chromosome that has both copied itself and coiled up into this nice fluffy shape. These are the “daughter” cells and each has its own copy of all the DNA—They are clones of the “mother” cell and identical to each other in all ways.

  5. Clearing up the confusion! Remember, even though it is doubled they still call it a chromosome! The two copies are called sister chromatids

  6. It’s the same DNA; just at different stages of the cell cycle. Here the DNA is not as coiled so the ENTIRE nucleus is colored when the DNA is stained. Here the DNA is coiled tighter so only the chromosomes are colored and visible.

  7. Chromosomes and Genes • A gene is a short length of DNA on a chromosome which controls an inherited characteristic of the organism (It is the instruction for a single protein) • A chromosome carries a lot of genes (it is more like an instruction book) gene controlling skin colour gene controlling tongue rolling chromosome gene controlling eye colour gene controlling blood group

  8. Our Chromosomes: From uncoiled to coiled

  9. Each Human cell has 46 chromosomes • 22 pairs are essentially identical in both sexes One from Mom, one from Dad. Autosomes • The 23rd pair is different in males (They have an X and a Y chromosome) and females (they have two X’s). Sex chromosomes. Other species have different numbers of chromosomes: Horse - 64 A fern species - 1200 Flatworm - 16 Fruit Fly - 8 Male ants - 1

  10. 2 major parts of the cell cycle • The cells grow, lots of extra proteins are made, and organelles (such as the mitochondria) and DNA replicate to prepare for cell division. • The cell divides (mitosis) resulting in two identical daughter cells (clones).

  11. The Cell Cycle • Cells are either Growing • (G phase) • Synthesizing new DNA • (S phase) • 0r dividing by Mitosis • (M phase) • M phase has four parts: • Prophase, Metaphase, Anaphase and Telophase. • The G and the S phases are collectively called the Interphase

  12. Interphase (Resting and growing stage) • Chromosomes cannot be seen. • Cells grow. • Chromosomes duplicate. • How do the chromosomes duplicate?

  13. Prophase nuclear membrane disappearing chromatids centromere • Chromosomes condense and become visible • Each chromosome consists of two identical sister chromatids. homologous chromosomes

  14. Metaphase • Chromosomes line up at the equator (centre of the cell) • Spindles are formed to attach to the center of each chromosome

  15. Anaphase chromosomes • Sister chromatids separate as individual chromosomes • They move apart towards the opposite poles

  16. Telophase nuclear membrane forming • Chromosomes gradually disappear • Nuclear membrane is formed around each set of chromosomes

  17. Can you identify the different stages of mitosis from the diagram below? anaphase interphase telophase metaphase prophase

  18. Summary of Mitosis Summary of Mitosis

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