Mitosis and binary fission

• What happens in interphase in mitosis?

  G1- (longest phase) -protein synthesis. The cell grows and volume of cytoplasm increases. cell differentiation(switching on or off of gene) If the cell is not going to divide again it remains in this phase. S-synthesis phase (replication phase) DNA replication occurs. It only enters this phase if the cell division is to follow. G2-(second growth phase) short-cytoskeleton of cell breaks down. Microtubule components begin to reassemble into spindle fibres which are required for cell division
• What happens in prophase?

  chromosomes condense and the nuclear envelope breaks down. chromosomes lie freely in cytoplasm. chromosomes move to opposite ends of the cell, forming protein fibres across it called a spindle

  
• What happens in metaphase?

  Chromosomes line up along equator. Spindle fibres from each pole become attached to the centrome of the chromosomes.

  
• What happens in anaphase?

  The spindles contract and pull the chromatids to each pole of the cell creating a v-shape.

  
• What happens in telophase?

  chromosomes become long and thin again. Spindle fibers break down. Nuclear envelope forms around each group of chromosomes. Then cytokinesis forms two individual cells

  
• What is poptosis?

  Cell suicide, body kills cellthe lysomes burst and cell structure is reusedif happens too much then organ damage happens which is called necrosistoo much can cause cancer which is called oncogenes
• What is the mitotic index?

  The mitotic index is how many cells are undergoing mitosis at any one time.number of cells with condensed chromosomes/total number of cells x100
• how does a prokarytotic cell divide?

  Prokaryotic cells divide by binary fission. The DNA molecule and plasmids replicate. The cell membrane grows and pinches inwards to divide the cytoplasm into two. A new cell wall forms dividing the cell into two identical daughter cells.
• How do viruses replicate?

  Viruses are not cells and so cannot replicate by cell division. Instead they insert their nucleic acid into the host cell. This provides instructions for the host cell to create and assemble all of the components of the virus.
• How is cancer treated?

  Cancer is treated by killing the cells in the tumour by disrupting the cell cycle. Cancer drugs either prevent DNA from replicating or inhibit metaphase by disrupting spindle formation.
• Describe Binary fission in bacteria

  Circular DNA is first replicated. Then plasmids are replicated. The cytoplasm is then divided, producing two daughter cells each with a single copy of circular DNA and copies of plasmids