New cells

New cells

1. Cell cycle

   • the events as a parent cell splits into two genetically identical daughter cells.

2. Copying and seperating

   • Checks and balances - as chromosomes replicate, enzymes check DNA strands for inprecise copying, which could result in mutations, and the cell failing to function
   • G1 = growth ocurs and organelles replicate +proteins are made, then biosynthesis occurs, chromosomes can be replicated to produce two exact copies attached at the centromere, called a pair of sister chromatids
     • the G2 occurs - growth occurs in prep for cell division, leading onto mitosis
   • Before division chromatin supercoil to form visible chromosomes, they cannot perform their normal functions like this so must uncoil ASAP

3. Mitosis

   • Prophase - chromsomes become supercoiled - so are visible.
     • Centrioles divide into two
     • Each daughter centriole moves to poles of cell to form spindle
   • Metaphase - chromosomes move to central region of the spindle (equator)
   • They attach to spindle equator by centromere
     • Anaphase- Sister chromatids split at centromere
       • Spindle threads shorten pulling sister chromatids apart towards poles
       • They assume a V shape - centromere leads
       • telophase - chromatids now chromosomes (nuclear envelope forms around each one)
         • Spindle disappears + chromosomes uncoil (now cant be seen)
         • now cell splits via cytokinesis - two new cells are genetically identical
           • Cytokinesis starts from outside in animal cells (and nip in) but plant cell cytokinesis starts with the formation of a cell plate where the spindle equator was.
             • new cell membrane and new cell wall material is laid down along this cell plate
   • the process of nuclear division where two genetically identical nuclei are formed from one parent cell nucleus
   • The nuclear envelope breaks down
   • Mitosis in plant cell
     • only meristem cells divide
     • plant cells do not have centrioles, the tubulin protein threads are made in the cytoskeleton

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