meiosis and mitosis

• DNA is the hereditary material in living organisms, encoding genetic information essential for growth, development and functioning
• chromosomes carry genetic information in the form of genes
• where are chromosomes found?


  in the nucleus
• what are chromosomes composed of?


  DNA and proteins
• chromosomes ensure proper DNA replication during cell division
• centromeres are the region of a chromosome where sister chromatids are joined
• centrioles are each of a pair of minute cylindrical organelles involved in the development of spindle fibres in cell division. these facilitate chromosome separation during meiosis/mitosis
• what are chromatids?


  one half of a duplicated chromosome, joined to its sister chromatid at the centromere
• during cell division, chromatids separate to ensure each daughter cell receives an identical set of genetic information
• what is the stage before the first stage in mitosis?

  interphase
• what happens during interphase?


  • the chromatid condenses into discreet chromosomes
  • the chromosomes replicate as the cell prepares for the next stages
  • organelles replicate and proteins synthesise
• what is the first stage of mitosis?


  prophase
• what happens during prophase?


  • chromatids coil up and become visible
  • centrioles replicate and move to poles of the cell
  • spindle fibre forms and attach
  • nuclear membrane begins to break down
• what is the second stage of mitosis?


  prometaphase
• what happens during prometaphase?


  • nuclear envelope breaks down completely which frees the sister chromatids from the nucleus
  • microtubules extend and form poles on either end of the cell and connect to the kinetochores
• what is stage three of mitosis?

  metaphase
• what happens during metaphase?


  • chromosomes are pulled by spindle fibres and line up in the centre of the cell
  • spindle fibres contract pulling the chromosomes apart
• what is stage four of mitosis?


  anaphase
• what happens during anaphase?


  • chromosomes are split into two and start to move to either pole of the cell
  • centromeres repel each other and are drawn to either end of the cell
  • the once circular cell now becomes stretched and cleavage furrow just begins to form
  • each end now has to completely different set of chromosomes
• what is the fifth stage of mitosis?


  telophase
• what happens during telophase?


  • nuclear membrane reappears at each pole
  • spindles disappear and the cleavage furrow is fully formed
  • chromosomes now uncoil and the cell returns to the interphase stage
  • once movement is complete, each cell has a diploid number of chromosomes
• what is the final stage of mitosis?


  cytokinesis
• what happens during cytokinesis?


  two diploid daughter cells form as the cytoplasm divides
• somatic refers to the body cells of an organism, these cells make up tissues and organisms, supporting life functions. any cell that is not a productive cell
• what does haploid mean?


  it refers to a cell or organism with a single set of chromosomes
• what does diploid mean?


  a cell or organism with two sets of chromosomes
• poles refer to the opposite ends of a cell or structure
• chromosomes hold all the information required to build an organism/
• every chromosome replicates to form a pair of identical sister chromatids, that are linked by a specialised DNA sequence known as a centromere
• what are the functions of cell division?


  • growth
  • repair
  • asexual reproduction
  • sexual reproduction
• mitosis produces and exact copy of the cell
• what are the functions of mitosis?


  • growth
  • repair
  • asexual reproduction
• meiosis produces gametes (sex cells)
• what is the function of meiosis?


  sexual reproduction
• mitosis is nuclear division, at the end of telophase, cytokinesis occurs where the cytoplasm divides
• in mitosis, each daughter cell is genetically identical to each other and has the same number of chromosomes as the parent cell