Mitosis

• What does mitosis do

  Mitosis is the division of the nucleus. Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication.
• which cells can divide In multicellular organisms

  Not all cells divide in multicellular organisms. Some cells retain the ability to divide and show a cell cycle.
• when does DNA replication occur in the cell cycle

  during the S- phase of interphase
• what is the role of spindle fibres in mitosis

  The spindle fibres attach to the centromeres of the chromosomes;

  The spindle fibres shorten, which leads to the separation of centromeres and moves chromatids to opposite poles of the cell.
• what is the role of the centromere in mitosis

  Holds chromatids together; Attaches chromatids to spindle; Allows chromatids to be move to opposite poles when the centromere splits
• what is cytokinesis 


  division of the cytoplasm and formation of a new cell membrane between cells
• what is the cell cycle describe each stage

  Eukaryotic cells that retain the ability to divide show a cell cycle which consists of: interphase, mitosis then cytokinesis.

  G1- cell grows and forms new organelle and proteins

  S-DNA replication occurs

  G2-Cell continues to grow and makes proteins needed for cell division. DNA is checked for errors (mutations).

  Mitosis- division of the nucleus
• describe the behaviour of chromosomes during interphase

  A period of cellular activity, increasing the size of cytoplasm and number of organelles. DNA is replicated, but not condensed into visible chromosomes.
• describe the behaviour of chromosomes and the cell during prophase

  Chromosomes condense, thicken and become

  visible. They appear as two sister chromatids held

  together by a centromere. The centrioles migrate

  to the opposite poles of the cell and form spindle

  fibres. The nuclear envelope disapears
• describe the behaviour of chromosomes and the cell during metaphase

  All the chromosomes line up on the equator of the

  up on the equator. Chromosomes are attached to spindle fibres;

  By their centromere;
• describe the behaviour of chromosomes and the cell during anaphase

  The spindle fibres contract and the centromere divides; chromatids are pulled to opposite poles of the cell;
• describe the behaviour of chromosomes and the cell during telophase

  Chromosomes uncoil and become longer, thinner. The nuclear membranes begin to form around the daughter nuclei, cytokinesis begins.
• explain how to calculate the mitotic index

  number of cells in mitosis / total number of cells
• explain how to calculate the number of cells that there will be after a period of time undergoing cell division

  2n X the starting number of cells

  N = the number of times cell division has occurred. This can be found

  out by multiplying the mitotic index by the total time period (to find the proportion of time cells are in mitosis) OR you may be given the length of the cell cycle and can then divide the total period of time by the length of one cell cycle.