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1.6 - Cell Division PPT (COPY).pptx - Understandings...

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Understandings
Applications and Skills
1.6U1: Mitosis is division of the nucleus intotwo genetically identical daughter nucleiWhy do cells divide?Remember: large cells have low SA:V ratiolessefficientIf an organisms grows larger, it need more cells,AND cells need to have a copy of the organism’sDNACell division allows forgrowthof the organisms byproducing more cells, and it also allows for morecell differentiationto occurMitosis occurs most frequently indevelopingembryosNew cells are also needed on a regular basis toreplacedead, damaged, or infected cellsCell division (specifically through mitosis) is alsoused inasexual reproduction(self-replication)
1.6U1: Mitosis is division of the nucleus intotwo genetically identical daughter nucleiGrowth- multicellular organisms increase their size byincreasing their number of cells via mitosisAsexual Reproduction- certain eukaryotic organims myreproduce asexually via mitosis (e.g. vegetativereproduction)Tissue Repair- replacing dead/damaged cellsEmbryonic Development- a fertilized egg (zygote) willundergo mitosis and differentiation in order to develop intoan embryo
1.6U1: Mitosis is division of the nucleus intotwo genetically identical daughter nucleiCell cycle- seriesof events throughwhich cells passto divide andcreate twoidentical daughtercellsInterphaseProphaseMetaphaseAnaphaseTelophaseCytokinesis
1.6U2: Chromosomes condense by supercoilingduring mitosisEvery eukaryote has genes on chromosomes - storage units in thenucleusEach chromosome has a partner (homologous chromosomes) -one from each parent.Both copies are required for the cell tofunction.Different species have different chromosome numbers:Humans = 23 pairs (n = 23)Diploid number (2n) = 46Frogs = 13 pairs (n = 13, 2n = 26)Corn = 10 pairs (n = 10, 2n = 20)Dogs = 39 pairs (n = 39, 2n = 78)Gametes(sex cells - sperm and eggs) arehaploid (n).They have ahalf setof chromosomes, as they will pair up with the other half infertilization.
1.6U2: Chromosomes condense by supercoilingduring mitosis
1.6U2: Chromosomes condense by supercoilingduring mitosis
1.6U2: Chromosomes condense by supercoilingduring mitosisWhy do chromosomes supercoil?Human cells are on average 1m0?in diameter and the nucleus withineach is less thanm in diameter.5?Human chromosomes are 15mmto 85mm (15,00m to0?85,00m) in length0?Chromosomes need to be storedcompactly to fit within the nucleiof cellsThis problem becomes more acuteduring mitosis when chromosomesneed to be short and compactenough that they can be separatedand moved to each end of the cell
1.6U2: Chromosomes condense by supercoilingduring mitosisHow chromosomes supercoil?Strain is places on a DNA helix by overwinding orunderwinding of the helixThis causes the DNA molecule to coil back on itselfbecoming shorter and widerNote: in eukaryotes, proteins called histones aid the process
1.6U4: Interphase is a very active phase of the cell cycle withmany processes occurring in the nucleus and cytoplasm

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