Rebecca Davenport BIOL 1406 11 14 16 Ch 12 blueprint 1 Cell cycle a b Key roles of cell division 1 Cell division Replicates entire DNA for daughter cells the two sets of DNA separate into two daughter cells ii Unicellular organisms reproduces the entire organism iii Multicellular eukaryotes depend on cell division for 1 Development from a fertilized cell 2 Growth Development 3 Repair iv Cell division is an integral part of the cell cycle the life of a cell from formation to its own division c Cell division results in genetically identical daughter cells i Mitosis copy and paste mechanism so cell division as a form of asexual reproduction create daughter cells that are genetically identical to parents called Clones ii Cell division results in daughter cells with identical genetic information 1 Chromosomes what DNA molecules in a cell are packaged into 2 Chromatin are what chromosomes consist of which condenses during cell division 3 iii Somatic cells nonreproductive cells have two sets of chromosomes 1 Undergo mitosis iv Gametes reproductive cells sperm and eggs have half as many chromosomes as somatic cells 1 Undergo meiosis v d Distribution of chromosomes during eukaryotic cell division i They will take their genome just need one copy of genome duplicate it move it to opposite ends of cell so when cell divides in half each daughter has a copy ii When we have just one copy of genome we call them Chromosomes when we have replicated chromosomes we call them sister chromatins these are identical we need them so each daughter cell will have one e Mitotic spindle i Mitotic spindle a structure of microtubules MT that controls chromosome movement during mitosis form in the centrosome ii Spindle includes centrosomes spindle microtubules and asters f iii Phases of the cell cycle i Interphase cell growth copying of chromosomes happens before mitotic phase 1 G1 phase first gap growth making proteins to do it s job 2 S phase synthesis replicate DNA 3 G2 phase second gap continued growth to prepare for cell division i ii Chromosomes not chromatin iii Microtubules originate from centrosomes 4 Cell grows during all 3 subphases chromosomes are duplicated only during the S phase ii Mitotic M phase cell division 1 Mitosis the division of the genetic material in the nucleus i Happens after interphase ii Asexual reproduction iii Only has one round of reproduction iv Somatic cells v Daughter cells will be identical to parents called clones 1 Diploid cell will produce Diploid 2 Haploid cell produces haploid 2 Prophase form mitotic spindle moves DNA to opposite ends of cell forming sister chromatins i Prometaphase will be prophase on exam nuclear envelope fragments so we can gain access to sister chromatins 1 Kinetochore microtubules attached to sister chromatins 2 Non kinetochore microtubules Polar do not attach to sister chromatins 3 3 Metaphase all sister chromatins are attached to spindles lined up neat in the middle called the metaphase plate i Sister chromatins are attached via cohesions proteins ii 4 Anaphase cohesions are split chromatins are pulled towards opposite sides of cell the cell is also elongating i 5 Telophase spindle breaks down and nuclear envelope is reformed DNA uncondenses spaghetti form i 6 2 Cytokinesis the division of the cytoplasm Happens after mitosis 1 In animal cells it occurs by a process known as cleavage forming a cleavage furrow 2 In plant cells a cell plate forms 3 g Binary fission in Bacteria i h Control system i The cell cycle appears to be driven by specific chemical signals present in the cytoplasm ii The sequential events of the cell cycle are directed by a distinct cell cycle control system which is similar to a clock iii The cell cycle control system is regulated by both internal and external controls iv The clock has specific checkpoints where the cell cycle stops until a go ahead signal is received G1 G2 and M phases v Cancer cells manage to escape the usual controls on the cell cycle i vi Cell cycle clock i Two types of regulatory proteins are involved in cell cycle control cyclins and cyclin dependent kinases Cdks 1 They check status internally of cell 2 ii The activity of a Cdk rises and falls with changes in concentration of its cyclin partner iii MPF maturation promoting factor is a cyclin Cdk complex that triggers a cell s passage past the G2 checkpoint into the M phase iv Stop and go signs internal and external signals at the checkpoints 1 Many signals registered at checkpoints come from cellular surveillance mechanisms within the cell 2 Checkpoints also register signals from outside the cell 3 Three important checkpoints are those in G1 G2 and M phases 4 For many cells the G1 checkpoint restriction checkpoint seems to be the most important 5 If a cell receives a go ahead signal at the G1 checkpoint it will usually complete the S G2 and M phases and divide 6 If the cell does not receive the go ahead signal it will exit the cycle switching into a non dividing state called the G0 phase v Loss of cell cycle controls in cancer cells 1 Cancer cells do not respond normally to the body s control mechanisms 2 Cancer cells may not need growth factors to grow and divide 3 They may make their own growth factor 4 They may convey a growth factor s signal without the presence of the growth factor 5 They may have an abnormal cell cycle control system 6 A normal cell is converted to a cancerous cell by a process called transformation 7 Cancer cells that are not eliminated by the immune system form tumors masses of abnormal cells within otherwise normal tissue 8 If abnormal cells remain only at the original site the lump is called a benign tumor 9 Malignant tumors invade surrounding tissues and can metastasize exporting cancer cells to other parts of the body where they may form additional tumors
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