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Cell Divisions

Cell Divisions. Mitosis and Meiosis. Mitosis. Division of the nucleus of all cells except sex cells Produces 2 daughter cells each with the same amount and type of genetic material as the parent cell. Synthesis. Also called Interphase of the cell cycle Not technically part of Mitosis

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Cell Divisions

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  1. Cell Divisions Mitosis and Meiosis

  2. Mitosis • Division of the nucleus of all cells except sex cells • Produces 2 daughter cells each with the same amount and type of genetic material as the parent cell

  3. Synthesis • Also called Interphase of the cell cycle • Not technically part of Mitosis • DNA is replicated (copied) to make an exact copy of itself • Each “new” strand is 1/2 of the “old” strand and 1/2 of newly formed strand

  4. Prophase • 1st stage of Mitosis • Nuclear membrane begins to weaken

  5. Prophase • Centrioles (Protein structures) form and move to the poles of the nucleus

  6. Metaphase • Chromosomes line up in the middle • Spindle fibers extend from the centrioles to the centromeres

  7. Anaphase • Spindle fibers shorten • Chromosomes are pulled apart at the centromere • Chromatids move to the opposite sides

  8. Telophase • Nuclear membranes begin to reform • Spindle fibers are gone • Centrioles begin to disassemble • Cleavage forms • Cleavage - an indentation in tissue

  9. Cytokinesis • Nuclear membrane complete • New cell membrane forms at cleavage • Exact copy of the original cell

  10. Cell Division for Sex Cells

  11. Meiosis • Division of the nucleus of sex cells • Produces 4 daughter cells each with the 1/2 amount and type of genetic material as the parent cell

  12. Meiosis • The first 1/2 is identical to Mitosis • Before the 2nd 1/2 the DNA is NOT replicated

  13. Prophase 1 of Meiosis • Nuclear membrane begins to dissolve • Centrioles begin to form and move to the poles

  14. Metaphase 1 of Meiosis • Chromosomes line up in the middle • Spindle fibers extend from the centrioles to the centromeres

  15. Anaphase 1 of Meiosis • Spindle fibers shorten • Chromosomes are pulled apart at the centromere • Chromatids move to the opposite sides

  16. Telophase 1 of Meiosis • Nuclear membranes begin to reform • Spindle fibers are gone • Centrioles begin to disassemble • Cleavage forms

  17. Cytokinesis 1 of Meiosis • Nuclear membrane complete • New cell membrane forms at cleavage • Exact copy of the original cell

  18. Metaphase 2 of Meiosis • Single copy of the chromosomes line up in the middle • Spindle fibers extend from the centrioles to the centromeres

  19. Anaphase 2 of Meiosis • Spindle fibers shorten • Single Chromosome is pulled apart at the centromere • Chromatids move to the opposite sides

  20. Telophase 2 of Meiosis • Nuclear membranes begin to reform • Spindle fibers are gone • Centrioles begin to disassemble • Cleavage forms on 4 new cells

  21. Cytokinesis 2 of Meiosis • Nuclear membranes complete • New cell membranes form at cleavage • 4 cells each with 1/2 the genetic information of the parent cell

  22. Mutations

  23. Mutations • Mutation: • Any change in the sequence (order) of the DNA • 3 main types • Insertion • Deletion • Substitution

  24. Results of Mutations • Benign - not good/not bad • This type of mutation leads to variations of traits • Different hair color, skin color, etc • Helpful • This type of mutation is beneficial to the organism • Harmful • This type of mutation interferes with normal protein production and often leads to illness or death

  25. Variation • A change in a trait which is caused by a change in the DNA

  26. Insertion Mutation • If the DNA were a sentence like: My sister is Betty Insertion would add 1 or more letters to the sentence: My sisters is Betty Bad grammar, but the sentence still makes sense

  27. Deletion Mutation • Using the same sentence: • My sister is Betty • Deletion mutation removes one or more letters • My sister is Btty • This can still makes sense, but changes the meaning of the sentence which in a cell could change the protein

  28. Problems with Insertion and Deletion Mutations • Once the message is carried out of the nucleus by RNA (we have not talked about this) all messages are read in 3 base segments • Adding or removing 1 base causes these segments to be completely changed

  29. Insertion and Deletion Continued • Using our sentence the 3 base sequences would look like this: • MYS IST ERI SBE TTY • Insertion would cause this: • MYS IST ERS ISB ETT Y • Deletion would cause this: • MYS IST ERI BTT Y

  30. Substitution Mutation • Still using the same sentence: • My sister is pretty • Substitution changes one or more letters • My mister is pretty

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