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Published byLeona Potter Modified over 5 years ago
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Biology is the only subject in which multiplication is the same thing as division…
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MITOSIS: Making New Cells Making New DNA
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Where it all began… We all start as a cell smaller than a period at the end of a sentence…
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And now look what can happen…
How did you get from there to here?
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Getting from there to here…
Going from egg to baby…. the original fertilized egg has to divide… and divide…
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Why do cells divide… One-celled organisms Multi-celled organisms
for reproduction asexual reproduction (clones) Multi-celled organisms for growth & development from fertilized egg to adult for repair & replacement replace cells that die from normal wear & tear or from injury amoeba starfish Unicellular organisms Cell division = reproduction Reproduces entire organism& increase population Multicellular organisms Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg Also use cell division to repair & renew cells that die from normal wear & tear or accidents
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Dividing cells… What has to be copied DNA organelles cell membrane
lots of other molecules enzymes plant cell animal cell
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Copying DNA A dividing cell duplicates its DNA
creates 2 copies of all DNA separates the 2 copies to opposite ends of the cell splits into 2 daughter cells But the DNA starts loosely wound in the nucleus If you tried to divide it like that, it could tangle & break DNA cell nucleus
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Copying & packaging DNA
When cell is ready to divide… copy DNA first, then… chromosomes COIL UP like thread on a spool… now can move DNA around cell without having it tangle & break Copying DNA Coil DNA into compact chromosomes
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Organizing & packaging DNA
cell nucleus DNA has been “wound up” DNA in chromosomes in everyday “working” cell cell nucleus 4 chromosomes in this organism DNA in chromosomes in cell getting ready to divide
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DNA must be duplicated…
chromosomes in cell 4 single-stranded chromosomes nucleus cell DNA in chromosomes nucleus cell duplicated chromosomes duplicated chromosomes 4 double-stranded chromosomes
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double-stranded human chromosomes
ready for mitosis
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Chromosomes of Human Female
23 pairs
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Chromosomes of Human Male
23 pairs
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Cell Cycle: Life Cycle of Cells
Stage 1: cell copies DNA DNA interphase cell nucleus
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Mitosis: Dividing DNA & cells
Stage 2: DNA winds up into chromosomes DNA is wound up into chromosomes to keep it organized duplicated chromosomes (prophase) cell nucleus
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Mitosis: Dividing DNA & cells
Stage 3: Chromosomes line up chromosomes line up in middle attached to protein “cables” that will help them move metaphase duplicated chromosomes lined up in middle of cell
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Mitosis: Dividing DNA & cells
Stage 4: Chromosomes separate chromosomes split, separating pairs start moving to opposite ends anaphase chromosomes split & move to opposite ends
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Mitosis: Dividing DNA & cells
Stage 5: Cell starts to divide cells start to divide nucleus forms again telophase
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Mitosis: Dividing DNA & cells
Stage 6: DNA unwinds again cells separate now they can do their every day jobs cytokinesis
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New “daughter” cells Get 2 exact copies of original cells same DNA
“clones”
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Cell division in Animals
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Mitosis in whitefish embryo
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Mitosis in plant cell
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onion root tip
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Please Make Another Two Cells
I.P.M.A.T.C. Overview of mitosis interphase prophase Please Make Another Two Cells cytokinesis metaphase anaphase telophase
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Any Questions??
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