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12 - The Cell Division Cycle
- 1. The Cell DivisionCycle Alena Prašnická
- 2. Cell division “Where acell arises, there must be a previous cell, just as animals can only arise from animals and plants from plants.” ◦ Rudolf Virchow in 1858 reproduction of cells is carried out as the sequence of reactions in which the cell duplicates its contents and divides into two cells - cell cycle
- 3. Cell division Unicellular organism •production of a complete new organism Multicellular organism • reproduction of individuals • embryonic development of the individuals • repair processes
- 4. Cell cycle basic function:duplicate accurately the amount of DNA in the chromosomes and distribute the copies into genetically identical daughter cells • duration of the cell cycle varies greatly from one cell type to another
- 5. Cell division inbacteria • one circular chromosome is attached to the plasma membrane Binary Fission • DNA replication • cell growth after doubling the size - simple division http://techhydra.com/science/biology/cel lular-biology/cell-division/binary-fission
- 6. Cell division –eucaryotic cell more complicated then cell division in bacteria • genetic information in nucleus • cytoskeleton • organelles
- 7. Chromosomes • a threadlikelinear strand of DNA and associated proteins in the nucleus of eukaryotic cells that carries the genes and functions in the transmission of hereditary information components: • DNA • acidic and basic protein Human - 46 chromosomes • 2 sets of 23 chromosomes • 22 pairs of autosomes (homologous chromosomes) and 2 sex chromosomes (X and Y)
- 8. Chromosomes the structure variesaccording to the phase of cycle - metaphase chromosome http://www.elu.sgul.ac.uk/rehash/guest/scorm/53/package/content/metaphase.htm
- 9. Cell cycle 4 phases G1phase S phase G2 phase M phase • Mitosis • Cytokinesis period between one M phase and the next one • interphase
- 10. Cell cycle G1 phase •from the english word gap – G phase • the first preparing phase • 30-40% of the cell cycle time
- 11. Cell cycle G1 phase •cell grows in size and synthesizes: RNA, proteins nucleotides enzymes for replication organelles mitochondia, chloroplasts, centriols ER, GA – fragmentation : distribution of organelles fragments forming organelles in the daughter cells GO phase
- 12. Cell cycle S phase •synthetic phase • nuclear DNA replication • 30-50% of the cell cycle time
- 13. Cell cycle DNA replication(duplication of DNA) semi-conservative
- 14. Cell cycle DNA replication(duplication of DNA) DNA synthesis begins at replication origin • binding of initiator protein • unwinding of DNA • binding other components of the replication complex DNA polymerase
- 15. Cell cycle Procaryotic cell •circular DNA • one replication origin
- 16. Cell cycle S phase synthesisof histones • simultaneously with the DNA synthesis • formation of nucleosomes and chromatin • in replicated DNA – histones • Centriols - Procentriols
- 17. Cell cycle G2 phase •the second preparing phase • 10-20% of the cell cycle time • cell continue in growing • synthesis of RNA, protein preparing for mitotic cell division
- 18. Cell cycle M phase •the last phase of the cell cycle • 5-10% of cell cycle time • chromosomes are replicated - sister chromatids • cell organelles are multiplicated cell is prepared for mitotic cell division
- 19. Cell cycle M phase •mitosis • cytokinesis
- 20. Mitosis Převzato a upraveno:https://en.wikipedia.org/wiki/Mitosis
- 21. Mitosis Prophase • chromatin condensation •formation of the mitotic spindle • formation of interpolar microtubules
- 22.
- 23. Mitosis Prometaphase • disassembling ofthe nuclear envelope • attached to them through specialized protein complexes – kinetochores
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- 25. Mitosis Metaphase • alignment ofchromosomes in the equator of the spindle (halfway between two spindle poles) - metaphase plate movement of chromosomes • continual growth and shrinkage of the microtubules – dynamic instability • microtubule motor proteins https://slideplayer.cz/slide/2588156/
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- 27. Mitosis Anaphase • segregation ofchromosomes - two identical sets of chromosomes Anaphase A – shortening of kinetochore tubules Anaphase B – spindle poles move apart
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- 29. Mitosis Telophase • nuclear envelopereassembles around each group of chromosomes two daughter nuclei decondensation of chromosomes - gene transcription can start again https://slideplayer.cz/slide/2588156/
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- 31. Cytokinesis • the cytoplasmis cleaved in two • begins in anaphase but is not completed until the two daughter nuclei have formed in telophase Plant cell X Animal cell
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- 33. Cytokinesis – animalcell during anaphase is formed cleavage furrow • vertical to the axis of the mitotic spindle • formed between the two groups of daughter chromosomes contractile ring • composed mainly of actin filaments and myosin filaments • divides cell into two daugther cells
- 34. Cytokinesis – animalcell symmetric cytokinesis = symmetric division of cytoplasm together with organelles • distribution of organelles – random
- 35. Cytokinesis – plantcell https://www.youtube.com/watch?v=C6hn3sA0ip0&list=UUcSThfV7yiW9I5hXBnEk9Zg
- 36. Cytokinesis – plantcell plant cell – cell wall • new cell wall starts to assemble in the cytoplasm between the two sets of segregated chromosomes at the start of telophase Phragmoplast - a structure that is formed in the equator of the old mitotic spindle • along microtubules are transported vesicles carrying material for the wall derived from the Golgi apparatus carry polysaccharides, glycoproteins • grows from the center towards the cell surface
- 37. Meiosis • type ofcell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells • meiosis begins in specialized diploid germ-line cells in the ovaries or testes these cells contain two copies of each chromosome, one inherited from the father organism (the paternal homolog) and one from mother (the maternal homolog) – homologous chromosomes Gamete cell - haploid cell n – single set of chromosomes Somatic cell - diploid cell 2n – two sets of chromosomes, one from the mother and the other from the father
- 38. Meiosis • one DNAreplication is followed by two rounds of cell division to produce four daughter cells two successive cell divisions • first meiotic division – meiosis I • second meiotic division – meiosis II
- 39. Meiosis Meiosis I Prophase • takesplace in the nucleus with an intact membrane – only chromosomes undergo changes 5 phases ◦ Leptotene ◦ Zygotene ◦ Pachytene ◦ Diplotene ◦ Diakinesis
- 40. Meiosis Leptotene • chromosomes condense •sister chromatids - tightly bound and indistinguishable from one another Zygotene • pairing of homologous chromosomes – bivalent • contains 4 chromatides • chromatids are associated by synaptonemal complex
- 41. Meiosis Pachytene • bivalent consistsof four sister chromatids nonsister chromatids of homologous chromosomes may exchange segments - Crossing-over • multienzyme systems responsible for chromatid recombination – in synaptonemal complex
- 42. Meiosis Crossing over nonsister chromatidexchange sections • chiasma - connection that corresponds to a crossover between two non-sister chromatids • many bivalents contain more than one chiasma - multiple crossovers
- 43. Meiosis Diplotene • degradation ofsynaptonemal complex and partial separation of homologous chromosomes Diakinesis • nuclear envelope begins to disappear • centrosomes are moving towards the poles of the cell
- 44. Meiosis Meiosis I Metaphase • bivalentsare moved to the equator • centromeres of chromosomes are randomly oriented to one or the other pole of cells • kinetochore microtubules connect bivalents to centromeres (spindle poles)
- 45. Meiosis Meiosis I Anaphase • segregationof homologous chromosomes - destrucion of bivalents • complete set of chromosomes formed by recombination from the original maternal and paternal chromosomes gets to each pole of the cell
- 46.
- 47. Meiosis Meiosis I Telophase • finishthe division of nucleus and cytokinesis
- 48. Meiosis Meiosis II • occurswithout further DNA replication and without any significant interphase period 4 haploid cells
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- 51. Cellular differentiation • multicellularorganisms consist of cells structurally and functionally different • the process of specialization - differentiation
- 52. Cellular differentiation genetic basisof differentiation • all cells have same genetic background – genetic information for all types of differentiated cells is in zygote
- 53. Cellular differentiation levels ofdifferentiation molecular - plasma membranes of various differentiated cells contain different receptor proteins - enabling different answers enzyme - production of specific metabolites - specific metabolic pathways morphological - changes in the shape and structure of cells • may lead to the elimination of vital structures - Erythrocytes • cell loses its ability to divide - terminal differentiation
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- 55. Cellular differentiation irreversibility ofdifferentiation ?? • dedifferentiation in plants - a plant callus can evolve whole plant • partial dedifferentiation - tissue regeneration the subject of intense research
- 56. Thank you foryour attention