2Essential Knowledge3.a.2 – In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis, or meiosis plus fertilization ( ).
3Roles of Cell Division Reproduction (uni vs. multi) Growth Repair/replace old or damaged cellsTo distribute identical genetic material to two new daughter cellsGoal: To split the sister chromatids and give one to each new cell – to make two new cells with the correct amount of genetic info
4Two cell types Somatic Sex Non-sex cells (all body cells EXCEPT sex) Ex: red blood, skin, muscleSexOtherwise known as gametesEx: sperm, egg
5Genome The cell's hereditary endowment of DNA Usually packaged into chromosomes (easier to manage during the cell cycle)Prokaryotes:Single stranded, in cytoplasm, circular in shapeEukaryotes:Double stranded, in nucleus, helix/spiral in shape
6Chromosomes Made of a DNA and protein complex called chromatin During cell division, the chromatin becomes highly condensed into the chromosomes# of chromosomes:Sex cell (haploid cell)23 (no pairs)—only contains one set of chromosomesSomatic cell (diploid cell)46 (in 23 pairs)—contain two sets of chromosomes
7Chromosomes vs. Chromatin Long, thin fiberUncondensedBefore/after cell divisionGenetic material usually in this formChromosomeCharacteristic “X” shapeCondensed into this shapeOnly during cell division
8Chromosomes - Structure At cell division, each chromosome has been duplicatedThe duplicated chromosome consists of two sister chromatidsCentromere – the point where two sister chromatids are connected
12Interphase - parts In order: G1 - first gap S - synthesis G2 - second gap
13G1, S, G2G1:Cell grows and carries out regular biochemical functionsS:DNA is replicated or synthesized - chromosomes are replicatedG2:Cell completes preparationsComment: A cell can complete S, but fail to enter G2.
14Mitotic Phase - parts1. Mitosis - division of replicated chromosomes 2. Cytokinesis - division of the cell’s cytoplasm
15Mitosis - Purpose To divide the 2 copies of the DNA equally To separate the sister chromatids into separate cells
16Mitosis Steps Prophase Prometaphase Metaphase Anaphase Telophase Mitosis Video #1Mitosis Video #2
24AnaphaseCentromeres break and the duplicate chromosomes are pulled away from each other toward opposite ends of the cellCell elongates; poles move slightly further apart
25KinetochoresSpecialized regions of the centromeres where spindle microtubules attachAppear to “ratchet” the chromosome down the spindle fiber microtubule using a motor proteinMicrotubules dissolve behind the kinetochore
30Cytokinesis – Animal vs. Plant Cleavage furrow formsMicrofilaments contracts and divides the cytoplasm into two partsPlantCell plate develops in between the two new daughter cells (from Golgi vesicles)New cell wall developed around the cell plate
44CDK and Cyclin CDK: Cyclin: Protein Kinase Amount remains constant during cycleInactive unless bound with cyclinCyclin:Protein whose concentration builds up over G1, S and G2When enough cyclin is present, active MPF is formed
45Active MPF Triggers Mitosis Activates a cyclin-degrading enzyme, which lowers the amount of cyclin in the cellResult - no active MPF to trigger another mitosis until the cycle is repeated
50Anchorage DependenceInhibition of cell division unless the cell is attached to a substratumPrevents cells from dividing and floating off in the body
51Cancer Cells Do not stop dividing. The control mechanisms for cell division have failed
52Cell division balanceRegulation of cell division is a balance between:Mitosis - making new cellsApoptosis - cell suicideCancer can result if either process doesn’t work
53Summary Identify the roles of cell division Identify the composition of a chromosome.Recognize the phases of the cell cycle.Identify the stages and characteristics of Interphase.Identify the stages and characteristics of Mitosis.Recognize the mechanisms of Cytokinesis.Recognize factors that control cell division.Recognize the results when the regulation of cell division goes wrong.