Mitosis And Meiosis

3,635 views

Published on

Cell division

Published in: Education, Technology
0 Comments
2 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
3,635
On SlideShare
0
From Embeds
0
Number of Embeds
8
Actions
Shares
0
Downloads
54
Comments
0
Likes
2
Embeds 0
No embeds

No notes for slide

Mitosis And Meiosis

  1. 1. <ul><li>Isaiah 61:1-3 </li></ul><ul><li>1 The Spirit of the Lord GOD is upon me; because the LORD hath anointed me to preach good tidings unto the meek; he hath sent me to bind up the brokenhearted, to proclaim liberty to the captives, and the opening of the prison to them that are bound; </li></ul><ul><li>2 To proclaim the acceptable year of the LORD, and the day of vengeance of our God; to comfort all that mourn; </li></ul><ul><li>3 To appoint unto them that mourn in Zion, to give unto them beauty for ashes, the oil of joy for mourning, the garment of praise for the spirit of heaviness; that they might be called trees of righteousness, the planting of the LORD, that he might be glorified. </li></ul>
  2. 2. Mitosis and Meiosis Timothy G. Standish, Ph. D.
  3. 3. Mitosis: In The Beginning One <ul><li>Most of the organisms we see started out as one cell </li></ul><ul><li>Humans start out as a single cell, the zygote, formed by uniting a sperm and egg </li></ul><ul><li>The zygote divides to make approximately one trillion cells </li></ul><ul><li>During the process of dividing, cells become specialized to function in the various tissues and organs of the body </li></ul><ul><li>Mitosis is the process of cell division in eukaryotic cells </li></ul>
  4. 4. Fertilization Results In A Diploid Zygote Egg 1n Haploid nucleus Sperm 1n Haploid nucleus
  5. 5. Fertilization Results In A Diploid Zygote Sperm 1n Egg 1n Haploid nucleus Haploid nucleus
  6. 6. Fertilization Results In A Diploid Zygote Sperm 1n Egg 1n Haploid nucleus Haploid nucleus
  7. 7. Fertilization Results In A Diploid Zygote Sperm 1n Egg 1n Haploid nucleus Haploid nucleus
  8. 8. From Zygote to Embryo Zygote 2n Zygote 2n
  9. 9. From Zygote to Embryo Cleavage
  10. 10. From Zygote to Embryo Cleavage
  11. 11. From Zygote to Embryo Cleavage
  12. 12. From Zygote to Embryo Cleavage
  13. 13. From Zygote to Embryo Morula
  14. 14. Why Cells Must Divide <ul><li>In multi-celled organisms (like humans) cells specialize for specific functions thus the original cells must divide to produce different kinds of cells </li></ul><ul><li>Cells can only take in nutrients and excrete waste products over the surface of the membrane that surrounds them. The surface to volume ratio decreases with the square of the volume (unless special accommodations are made) </li></ul>2 cm Surface 24 cm 2 / volume 8 cm 3 = 3 1 cm Surface 6 cm 2 / volume 1cm 3 = 6
  15. 15. The Cell Lifecycle <ul><li>The cell lifecycle is well defined and can be divided into four stages: </li></ul><ul><ul><li>Gap 1 (G1) - The growth phase in which most cells are found most of the time </li></ul></ul><ul><ul><li>Synthesis (S) - During which new DNA is synthesized </li></ul></ul><ul><ul><li>Gap 2 (G2) - The period during which no transcription or translation occurs and final preparations for division are made </li></ul></ul><ul><ul><li>Mitosis - Cell division </li></ul></ul>
  16. 16. The Cell Life Cycle G1 M G2 S Gap 1 - Doubling of cell size. Regular cellular activities. transcription and translation etc. Synthesis of DNA - Regular cell activities cease and a copy of all nuclear DNA is made Gap 2 - Final preparation for division Mitosis - Cell division
  17. 17. Stages Of Mitosis <ul><li>During mitosis an exact copy of the genetic material in the “mother” cell must be distributed to each “daughter” cell </li></ul><ul><li>Each stage of mitosis is designed to achieve equal and exact distribution of the genetic material which has been copied during the S phase of the cell cycle </li></ul>
  18. 18. Stages Of Interphase <ul><li>Interphase - The in between stage - Originally interphase was thought to be a resting stage. Now we know that this is the stage most cells spend their time in as they do the things cells do including, if they are preparing to divide, growing and replicating their DNA </li></ul>G1 M G2 S Interphase
  19. 19. Stages Of Mitosis <ul><li>Prophase - The beginning phase - DNA which was unraveled and spread all over the nucleus is condensed and packaged </li></ul><ul><li>Metaphase - Middle stage - Condensed chromosomes line up along the equator of the cell </li></ul><ul><li>Anaphase - One copy of each chromosome moves to each pole of the cell </li></ul><ul><li>Telophase - End stage - New nuclear membranes are formed around the chromosomes and cytokinesis (cytoplasm division) occurs resulting in two daughter cells </li></ul>
  20. 20. Stages Of Mitosis Mother cell Interphase Anaphase Telophase Metaphase Mitotic spindle Prophase Nucleus with un-condensed chromosomes Equator of the cell Condensed chromosomes Disappearing nuclear membrane Poles of the cell Two daughter cells Metaphase plate
  21. 21. Packaging DNA B DNA Helix A T T A G C C G G C T A T A G C C G G C T A A T Histone proteins Histone octomer 2 nm
  22. 22. A T T A G C C G G C T A T A G C C G G C T A A T Packaging DNA B DNA Helix Histone octomer Histone proteins 2 nm
  23. 23. A T T A G C C G G C T A T A G C C G G C T A A T Packaging DNA Histone octomer B DNA Helix Histone proteins Nucleosome 11 nm 2 nm
  24. 24. Packaging DNA A T T A G C C G C G G C T A A T
  25. 25. Packaging DNA A T T A G C C G C G G C T A A T
  26. 26. Packaging DNA “ Beads on a string” Tight helical fiber Looped Domains A T T A G C C G C G G C T A A T Protein scaffold 11 nm 30 nm 200 nm
  27. 27. Packaging DNA Metaphase Chromosome G C A T Protein scaffold 700 nm 11 nm 30 nm 200 nm 2 nm Looped Domains Nucleosomes B DNA Helix Tight helical fiber
  28. 28. Chromosomes, Chromatids and Centromeres Centromere Chromosome arm Chromosome arm Two identical chromosomes Replication Identical chromatid Chromatid Anaphase A packaged chromosome
  29. 29. Chromosome Morphology Chromosomes can be distinguished on the basis of size and the relative location of centromeres. Chromosome arm Chromosome arm Centromere Submetacentric Acrocentric Telocentric Metacentric q arm p arm petite
  30. 30. Controlling The Cell Cycle <ul><li>CDC Mutants - Cell Division Cycle mutants helped elucidate genetic control points of the cell cycle </li></ul><ul><li>Three major checkpoints controlled by Cyclin dependant kinase (Cdk) proteins which add phosphates to cyclin proteins changing their activity: </li></ul><ul><li>G1S - Monitors cell size and checks for DNA damage </li></ul><ul><li>G2M - Ensures physiological conditions are right for division including completion of DNA replication and any necessary repair </li></ul><ul><li>M - Checks for successful formation of the mitotic spindle and attachment to the kinetochores </li></ul>
  31. 31. p53
  32. 32. Meiosis: In The Beginning Two <ul><li>Humans and many other complex multi-celled organisms incorporate genetic recombination in their reproduction </li></ul><ul><li>Reproduction in which there is a re-mixing of the genetic material is called sexual reproduction </li></ul><ul><li>Two cells, a sperm and an egg, unite to form a zygote, the single cell from which the organism develops </li></ul><ul><li>Meiosis is the process of producing sperm and eggs (gametes) </li></ul>
  33. 33. Gametes Are Haploid <ul><li>Gametes must have half the genetic material of a normal cell </li></ul><ul><li>If the genetic material in the gametes was not halved, when they combined the zygote would have more genetic material than the parents </li></ul><ul><li>Meiosis is specialized cell division resulting in cells with half the genetic material of the parents </li></ul><ul><li>Gametes have exactly one set of chromosomes, this state is called haploid (1n) </li></ul><ul><li>Regular cells have two sets of chromosomes, this state is called diploid (2n) </li></ul>
  34. 34. Stages Of Meiosis <ul><li>Meiosis resembles mitosis except that it is actually two divisions not one </li></ul><ul><li>These divisions are called Meiosis I and Meiosis II </li></ul><ul><li>Meiosis I results in haploid cells with chromosomes made up of two chromotids </li></ul><ul><li>Meiosis II is essentially mitosis on haploid cells </li></ul><ul><li>Stages of meiosis resemble mitosis with two critical differences: the first in prophase I and the second in Metaphase I </li></ul>
  35. 35. Stages Of Meiosis - Meiosis I <ul><li>Prophase I - The beginning phase - </li></ul><ul><ul><li>DNA which was unraveled and spread all over the nucleus is condensed and packaged </li></ul></ul><ul><ul><li>Homologous chromosomes (each made of two identical chromatids) come together and form tetrads (4 chromatids) </li></ul></ul><ul><ul><li>Crossing over , in which chromatids within tetrads exchange genetic material, occurs </li></ul></ul><ul><li>Metaphase I - Middle stage - Tetrads line up along the equator of the cell </li></ul>
  36. 36. Stages Of Meiosis - Meiosis I <ul><li>Anaphase I - One copy of each chromosome still composed of two chromatids moves to each pole of the cell </li></ul><ul><li>Telophase I - End stage - New nuclear membranes are formed around the chromosomes and cytokinesis (cytoplasm division) occurs resulting in two haploid daughter cells </li></ul>
  37. 37. Stages Of Meiosis - Meiosis II <ul><li>Prophase II - Cells do not typically go into interphase between meiosis I and II, thus chromosomes are already condensed </li></ul><ul><li>Metaphase II - Chromosomes line up at the equator of the two haploid cells produced in meiosis I </li></ul><ul><li>Anaphase II - Chromosomes made up of two chromatids split to make chromosomes with one chromatid which migrate to the poles of the cells </li></ul><ul><li>Telophase II - Cytokinesis and reformation of the nuclear membrane in haploid cells each with one set of chromosomes made of one chromatid </li></ul>
  38. 38. Stages Of Meiosis: Meiosis I Interphase Mother cell Meiosis II Prophase I: Tetrad formation/ crossing over Metaphase I Telophase I Prophase I: Condensing Chromosomes Anaphase I
  39. 39. Stages Of Meiosis: Meiosis II Telophase I The products of mitosis are 2 diploid cells with identical chromosomes. The products of meiosis are 4 haploid cells each with a unique set of chromosomes. Prophase II Metaphase II Anaphase II Telophase II
  40. 40. Crossing Over Because of crossing over, every gamete receives a unique set of genetic information. Prophase I: Tetrad formation/ crossing over Anaphase I Telophase II Metaphase I Telophase I
  41. 41. The End

×