division + differentiation in human cells

• A somatic cell is any cell in the body other than cells involved in reproduction
• Germline cells are gametes (sperm and ova) and the stem cells that divide to form gametes
• Somatic stem cells divide by mitosis to form more somatic cells.

  
  

  Germline stem cells divide by mitosis and meiosis.
• Cellular differentiation is the process by which a cell expresses certain genes to produce proteins characteristic for that type of cell
• Cancer cells divide excessively because they do not respond to regulatory signals.
• Cells within a tumour may fail to attach to each other, spreading the body where they may form secondary tumours.
• Each triplet of bases on mRNA is known as a codon and codes for 1 specific amino acid.
• Diploid cells have twenty-three homologous chromosomes.
• In Germline cells, Division by Mitosis produces more germline stem cells, and division by Meiosis produces haploid gametes.
• A haploid gamete contains twenty-three single chromosomes.
• Embryonic stems cells are therefore pluripotent as they can differentiate into any cell type.
• As Tissue stem cells can only differentiate into cells of that particular tissue type, they are multipotent.
• Use of embryonic stem cells can offer effective treatments for disease and injury; however, it involves the destruction of embryos.
• Stem cell research provides information on cell processes such as cell growth, differentiation and gene regulation. Stem cells are used as model cells to study how diseases develop or being used in drug testing.
• The therapeutic uses of stem cells involve the repair of damaged or diseased organs or tissues. Under the right conditions, in the laboratory, embryonic stem cells can self-renew.
• Mitosis = Diploid

  Meiosis = Haploid
• Some genes in cells are switched on and others are switched off. We say that the genes that have been switched on are 'expressed' by that particular cell
• TISSUE STEM CELL EXAMPLE:

  Blood stem cells located in bone marrow can give rise to red blood cells, platelets, phagocytes and lymphocytes.
• All genes in embryonic stem cells can be switched on so these can differentiate into any cell type
• Severely reduced numbers of lymphocytes can be treated by a bone marrow transplant because stem cells can differentiate into lymphocytes.
• Blood stem cells in the body are located in bone marrow.