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Cell division

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Practice PPT for Embeded PPT in Wiki Space for Mitosis and Meiosis College Prep Project.

Practice PPT for Embeded PPT in Wiki Space for Mitosis and Meiosis College Prep Project.

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  • 1. Cell Division
  • 2. Cells
    • Somatic
    • Regular Cells
    • Have 46 Chromosomes
    • 2N Diploid – set of chromosomes (two genomes)
    • Gametes
    • Sex Cells (egg/sperm; Pollen (sperm)/ovule (eggs)
    • Have 23 Chromosomes
    • N Haploid – one chromosome (a genome)
  • 3. Cell Cycle
    • The cycle of growth, mitosis and cytokinesis.
  • 4. Interphase
    • The longest phase of the cell cycle
    • Gap one- Cell prepares for DNA and chromosome replication
    • Synthesis- the DNA is replicated giving two exact copies called sister chromatids.
    • Gap two- cell grows for division and organelles duplicate.
  • 5. Mitosis
  • 6. Early Prophase
    • The DNA and proteins condense and become visible.
    • Centrioles begin to move apart.
    • Nuclear envelope begins to disappear.
  • 7. Late Prophase
    • Centrioles are on opposite sides of the nucleus.
    • Microtubules called spindle fibers begin to form.
    • Chromosomes are in homologous pairs.
    • Nuclear envelope is gone.
  • 8. Metaphase
    • Homologous Pairs held by a centromere.
    • The Kinetochores allow the spindle fibers to attach at the centromere
    • The spindle fibers push and pull the homologous pairs to the middle of the cell called the metaphase plate.
  • 9. Anaphase
    • The centromeres split and daughter chromosomes migrate to opposite ends of the poles.
    • Centrioles and spindle fibers pull the daughter chromosomes towards the poles.
    • Cytokinesis begins
    Late anaphase
  • 10. Telophase
    • Nuclear envelope begins to reform around each group of chromosomes.
    • Chromosomes begin to become less visible.
    • Cytokinesis pinches in and cell membrane or cell plate begins to form.
    Animal Cell Plant Cell Cell Membrane
  • 11. Cytokinesis
    • The division of the cytoplasm.
    • This process compartmentalizes the two new nuclei into separate daughter cells.
    Animal Cell in Cleavage Furrow Cell Plate formation
  • 12. Mitosis
    • Maintains a constant amount of genetic material and a constant set of genes from generation to generation.
    • No genetic material is lost.
    • One copy of each duplicated chromosome segregates into a daughter cell.
    • 2 cells at end of Mitosis.
  • 13. Mitosis Chromosome #
    • If a parent cell is diploid, this results in two genetically identical progeny diploid cells, each with two sets of chromosomes.
    • Or
    • If the parent cell was haploid the daughter cells will also be haploid.
  • 14. Mitosis and Cancer
    • Cell division is controlled by specific chemical reactions that act as check points.
    • When these signals are ignored by a cell, cancerous cells occur.
    • Cancer is a disorder where the body cells lose control of the growth of the cell.
  • 15. Cells
    • Cells come from other cells.
    • When an organism develops progeny cells will begin to differentiate.
    • Cell differentiation means that the cells become specialized as the fetus develops
    • or
    • they express different segments of genes then other cells and develop into a new cell form.
  • 16. Cells
    • Cells have a lifespan.
    • Some cells become terminally differentiated, they will go through Apoptosis or death and will be replace by younger cells.
    • The younger cells come from stem cells, which are a cell in the tissue that can self-renew.
    • Stem cells change or differentiate into specialized cells.
  • 17. Cells
    • Totipotent- cells that have the ability to differentiate into any cell type. A true totipotent cell is the first cells in an zygote or fertilized egg.
    • Pluripotent can develop into many kinds of cells but not all.
    • Multipotent cells can produce only the type of cells that are unique to a tissue.
  • 18. Molecular Control of the Cell cycle – Internal Regulators
    • Checkpoints are in place at the different points in the cell cycle.
    • Checkpoints look for damaged cells to repair or terminate.
  • 19.
    • G1 to S – determines if cell is ready for Synthesis
    • G2-M – Checks for all DNA to be replicated and SA:V ratio is correct.
    • If environment is not favorable the cycle will stop.
    • M checkpoint – determines if the chromosomes are attached to the spindles for chromosome separation.
  • 20. Proteins are the Checkpoints
    • Cyclins (protein) and Kinases (enzyme) are the regulators to the cell cycle.
    • The regular chemical reactions between these molecules keeps the cycle active or inactive.
    • Complicated signaling system.
  • 21. External Regulators
    • Growth Factor- molecule that stimulates cell division
    • Growth Factors can come from hormones or from the cells around the dividing cells.
    • Healthy cells will only grow and divide when there is a balance between growth factor and inhibitory signals.
  • 22. Cancer
    • At current rates, over a third of the people who read your textbook will die of cancer 
    • Tumors or neoplasms are tissue masses caused from non-normal cell growth.
    • Benign – not life threatening
    • Malignant – life threatening and disruptive to other tissues.
  • 23.  
  • 24. Mitosis Review
    • Mitosis is for increasing cell number.
    • Mitosis is for individual organism growth and repair.
    • The loss of control of the Mitotic cycle leads to cancer.
    • The result is two identical cells with the same number of chromosomes as the Parent Cell.
    • In somatic cells – Nothing to do with heredity.
  • 25. Meiosis
    • Two successive divisions of a diploid nucleus with only one replication of DNA.
    • In animals the result is the formation of haploid gamete (gametogenesis)
  • 26. Meiosis I
    • First, interphase and DNA replication
    • Meiosis I is the first nuclear division.
    • Broken in to stages:
      • Prophase 1
      • Metaphase 1
      • Anaphase 1
      • Telophase 1
      • Cytokinesis
  • 27. Prophase 1 is Different in Meiosis
    • Homologous pairs exist (homologous is two sister chromatids connected at a centromere)
    Sister Chromatid Centromere
  • 28. Prophase 1
    • Synapsis: the formation along the length of the chromatids of a zipperlike structure which aligns the two homologs precisely, base pair by base pair.
  • 29. Prophase 1
    • Tetrad: four chromatids in a synapsed set of homologous chromosomes.
  • 30. Prophase 1
    • Crossing-over: the exchange of chromosome segments at corresponding positions along pairs of homologous chromosomes.
  • 31. Crossing-over
    • The exchange of corresponding genetic information produces new gene combinations in a population.
    • Usually, no loss of addition to the genetic material because it is a reciprocal exchange along the synapse.
    • Chiasma is the site at where the crossing-over occurred and is visible in late prophase 1.
  • 32. Recombination
    • A chromosome that emerges from meiosis with a combination of genes that differ from what the chromosomes started with is a recombinant chromosome.
    • This is important in genetic recombination - variety in genetics in a species.
  • 33. Prophase 1
    • After Genetic Recombination occurs the remaining steps in Prophase 1 are the same as Mitosis.
  • 34. Metaphase 1
    • The homologs line up two by two on the equatorial plane versus one by one in Mitosis.
  • 35. Anaphase 1
    • The tetrad separates, so that the homologous pairs disjoin and migrate toward a pole.
  • 36. Anaphase 1 Difference from Meiosis
    • At this time, the segregated sister chromatid pairs remain attached at the centromere.
    • Sister Chromatids stay together in meiosis, where as they would separate in Mitosis.
  • 37. Telophase 1
    • The nuclear envelope is formed around the homologous pairs.
    • Cytokinesis begins.
  • 38. Cytokinesis
    • Two cells that are 2N.
    • Ready to start Meiosis II
  • 39. Meiosis II
    • The second meiotic division similar to Mitosis.
  • 40. Meiosis II, What is Different?
    • The is no Interphase, NO SYNTHESIS of DNA.
    • You just go right into prophase II!
    • End products are 4 haploid cells from one original diploid cell.
    • Each progeny cell has one chromosome for each homologous pair of chromosomes.
  • 41. Meiosis II, What is the Difference?
    • The chromosomes are not exact copies of the original chromosomes due to recombination.
    • Recombination generated more variation in genetic combinations.
  • 42.  
  • 43. Independent Assortment
    • The factors for different traits assort independently of one another.
    • Basically this means, genes on different chromosomes separate independent of each other in Meiosis.
  • 44. Crossing-over and Independent Assortment.
    • If genes are located close together on a chromosome they have less chance to cross-over and assort independently.
    • If genes are located farther apart on the chromosomes they have are more likely to independently assort and recombine.
    • This can mean that some genes are almost always guaranteed to be on the same chromosome or found together (linkage).
  • 45. Read Chapter 10
  • 46. Chromosomes
    • Two Types: Autosomal and Sex
    • 22 Regular Autosomal Chromosomes and 2 Sex Chromosomes in Humans.
  • 47. Chromosome Structure
    • DNA/ Gene
    • Chromatin: sustainable material in a cell nucleus (DNA + Proteins)
      • Proteins – Histones and Nonhistones
      • Histones- Protein with positive charge that the DNA is atracted to and coild around it.
      • Nonhistone- Proteins that play various roles in DNA replication and determine physical structure of the chromosome.
  • 48. Chromosome Structure
    • Nucleosome: is the basic unit of the chromatin ( the DNA wrapped around the histone with linkers between histones.
    • The interactions between the histones make the DNA coil back onto itself to create a chromosome.
  • 49.  

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