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DNA and Cell Division

DNA and Cell Division. Mitosis in Animals. Background Information. Once an egg becomes fertilized, cellular divisions begins, eventually producing a whole organism. All cells derived from the zygote contain the same genetic material. An Integrated Organism. Organization of DNA.

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DNA and Cell Division

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  1. DNA and Cell Division

  2. Mitosis in Animals

  3. Background Information Once an egg becomes fertilized, cellular divisions begins, eventually producing a whole organism All cells derived from the zygote contain the same genetic material An Integrated Organism

  4. Organization of DNA • All cells have DNA (chromosomes). • Almost all cells divide for reproduction, growth or repair. • Each new cell needs the exact same DNA as the original cell. • The original cell is called the mother cell and the two new cells are called daughter cells. • The DNA in the nucleus must replicate before the cell divides.

  5. Chromosome Number in Different Species

  6. E. coli 4300 Yeast 6000 Roundworm 18,600 Fruit fly 13-14,000 Mosquito 13-14,000 Mouse 30-35,000 Human 30-35,000 Number of genes in sequenced genomes

  7. A non-dividing cell: • 90% of a cell’s life is spent growing, not dividing • This phase is called interphase • The DNA in this phase is not condensed; thus is chromatin • At some point during this phase the DNA is doubled or replicated • Two copies are made, one for each of the new cells

  8. Once replication occurs, the chromatin folds up to form chromosomes • This only occurs when the cell is about to divide • The duplicated chromosomes attach to each other at the centromere • Each individual copy of one chromosome is known as a chromatid • When chromatids are joined at the centromere, they are known as a single chromosome.

  9. sister chromatids centromere A piece of DNA or chromosome in an undividing cell Same piece now has replicated and super coiled ready for cell division.

  10. Also during interphase… • Additional organelles are produced • Cell membrane enlarged to allow cell growth • When the cell becomes too big to function it must divide • What would the SA/V ratio of this cell be…large or small?

  11. Interphase • The cell grows • New organelles are formed • Duplicate chromosomes are produced • The chromosomes are uncoiled and invisible • This uncoiled chromosomes are known as a chromatin

  12. Cell division/reproduction • Interphase is not considered to be part of cell reproduction. • It is simply the growth of the cell and the duplication of the chromosomes. • Cell reproduction consists of two separate stages known as mitosis and cytokinesis. • Cell division = mitosis + cytokinesis • A parent cell will produce 2 daughter cells.

  13. In cell division each chromosome is replicated and then the cell (and nucleus) divides

  14. Cell Reproduction • Original cell divides into two genetically identical daughter cells • Complete set of genetic information passed onto each daughter cell • DNA must be accurately duplicated before cell division • Mitosis: paired chromatids separate and move to opposite ends of the cell • Cytokinesis: cytoplasm + organelles divide into roughly equal halves

  15. http://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swfhttp://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swf Mitosis Animation

  16. MITOSIS/ CELL DIVISION • Stages include: • Prophase • Metaphase • Anaphase • Telophase

  17. Mitosis Nucleolus disappears; Nuclear envelope breaks down Duplicated chromosomes remain elongated Chromosomes condense and shorten LateInterphase EarlyProphase LateProphase Metaphase Centrioles have also been duplicated Microtubules attach to Centromeres Centromeres align at cell’s equator Centrioles begin to move apart; Spindle forms

  18. Mitosis: Cytoplasm divided along equator Spindle fibers pull chromatids to opposite poles Chromosomes begin unwinding NextInterphase Anaphase Telophase Cytokinesis Each daughter gets 1 nucleus & half of cytoplasm Nuclear envelope re-forms, spindle fibres disappear Chromatids become independent chromosomes

  19. Prophase • Chromatin condenses (into chromosomes) • Chromosomes appear as “X”s. • Nuclear envelope dissolves (DNA free in cell) • Animals cells only: Centrioles move to opposite ends of cell + form spindle fibers • Centromere attaches to spindle fibre

  20. Metaphase • Each chromosome lines up in the middle of the cell. • Highly organized so that both cells get exactly the same DNA. • Spindle fibers attached to centromeres of chromosomes

  21. Anaphase • Each pair of chromatids splits at the centromere • Each chromatid is now an individual chromosome • Paired chromosomes are pulled to opposite ends by spindle fibres

  22. Telophase • Chromosomes end up at separate poles, spindle fibers begin to dissolve. • New nuclear envelope begins to form around chromosomes • chromosomes begin to uncoil • Cell starts to pinch off through cytokinesis

  23. Cytokinesis • Division of all the rest of cell parts but not equally (organelles) • Animals: cell membrane pinches to form two cells • Plants: new cell plate created between the two cells (becomes cell wall)

  24. The Cell Cycle: An Overview 1)Interphase 2)Mitosis • Prophase • Metaphase • Anaphase • Telophase 3)Cytokinesis Cell Division (Cell Reproduction) = mitosis + cytokinesis

  25. Use an Acronym For Mitosis: • Prophase = P • Metaphase = M • Anaphase = A • Telophase = T Make a sentence: • Please MeetAt Ten • Phil, Mary, And Tom

  26. Figure 11-2

  27. Links • http://en.wikipedia.org/wiki/Trisomy#Trisomy • http://www.medgen.ubc.ca/wrobinson/mosaic/mos_how.htm

  28. Mitosis Drawing • Fold a large sheet of paper in 3 • You should have 3 columns on the front and 3 on the back • You will draw a cell in each stage of mitosis and include a written description of what is occurring at each stage • Stages: Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis • Notice that there are 6 stages and 6 coulmns on your sheet...1 stage per column!

  29. Some facts • 500,000 deaths per year (more males) • Older age group stricken more often • More than 100 types of cancer, many due to mutations triggered by environmental factors • Highest cancer incidence: male - prostate female - breast • Highest cancer deaths: lung

  30. Normal cells in culture • Organized structure • Limited cell growth • No overlapping

  31. Cancer cells in culture • Disorganized • Overlapping structure • Uncontrolled cell growth

  32. Some images to make this real: look first at normal skin

  33. Cancerous Skin

  34. What causes a normal cell to become a cancer cell?

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