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Understanding Mitosis and Meiosis: Cell Division Explained

Explore the processes of mitosis and meiosis, the two types of cell division crucial for life. Mitosis produces two identical daughter cells for growth and repair, while meiosis results in four genetically unique sex cells with half the chromosome number. This guide covers the stages of each process, including interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. Additionally, learn about mutations, their types, and their impacts on genetic variation, including insertion, deletion, and substitution mutations that affect DNA sequences.

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Understanding Mitosis and Meiosis: Cell Division Explained

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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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