2014 CELL DIVISION Výukový materiál MB Tvůrce: Mgr. Šárka Vopěnková Tvůrce anglické verze: ThMgr. Ing. Jiří Foller Projekt: S anglickým jazykem do dalších předmětů Registrační číslo: CZ.1.07/1.1.36/ Tento projekt je spolufinancován ESF a SR ČR

 entire cell = zygote  zygote divides repeatedly  developed cell differentiates > tissues > organs> organisms CELL DIVISION

 cells reproduce by division  division is anticipated by chromosome division = replication of DNA PROKARYOTIC CELL DIVISION

CELL CYCLE  the life period of the cell from its origin up to the development of daughter cells  the cell stops dividing > it accomplishes specific functions  liver cell divides once a year  neuron never divides  the most cells of human body undergo about 50 divisions and then they die

 cell cycle - 2 main phases: 1) cell division a) nuclear division: mitosis or meiosis b) cell division 2) interphase  90% of whole cell cycle  the cell grows up  in the nucleus there is chromatin > replication of DNA  interphase: G 1, S, G 2 phase CELL CYCLE

1. replication of DNA 2. cell division  cell cycle:  sequence of processes from the first to the second division PROKARYOTIC CELL DIVISION

REGULATION OF CELL CYCLE

 there are three of them: in the phases G1, G2, M  cells of mammals – the point in the G1 phase is obviously the most important  if the cell does not receive the signal „Ahead“ in G1 phase, it can get into G 0 phase.  the most cells of our body are in this phase CHECKPOINTS

INTERPHASE  G1 phase  metabolic activity  by the isolation of the daughter cell  the cell grows up  synthesis of RNA and proteins  main control nodal point  S phase synthetic  replications of DNA proceeds here:  DNA replicates up to double amount > chromosome is doubled since then:  created by a pair of sister chromatids  the cell is actually tetraploid

INTERPHASE  G2 phase  relatively short  metabolic activity  the cell grows up rapidly  reduplication of organelles  formation of structures necessary for the cell division

INTERPHASE G0 phase G0 phase  the phase when the cell does not divide any more  ending of the cell cycle  by differentiated cells  the beginning is influenced by the control  the beginning is influenced by the control nodal point  placed in the beginning G1 phase  fully differentiated cells (e.g.. neurons) do not divide any more  on the contrary e.g. liver cells - hepatocytes are able to go from G0 phase do G1 phase to start dividing again in the case of need

REGULATION OF THE CELL CYCLE  it proceeds through specific compounds  either stimulated and accelerated by the division (growth hormones, cytokinins)  or, on the contrary, they inhibit, stop (lack of nutrients, cytostatics)  all regulators influence the division in G1 phase = main control nodal point

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