Cell division + cells in medicine

• Your body is made up of cells.
• Each cell contains a nucleus which contains genetic information and controls the cell.
• Each nucleus contains lots of little thread-like structures called chromosomes.
• Chromosomes carry the genetic information which controls how your body works and what you look like, controlling your characteristics.
• There are 46 chromosomes in a human body cell (23 pairs).
• Each chromosome is made up of long coiled strand of a molecule called DNA.
• Each chromosome contains a large number of genes.
• Each gene is a section of DNA which codes for a protein molecule, which controls one characteristic.
• Gametes (sex cells) a haploid which means they have half a set of DNA
• Interphase:

  • Cell growth
  • Increase in the number of sub-cellular structures such as ribosomes and mitochondria
  • The DNA replicates to form two copies of each chromosome
• Mitosis:

  • Nuclear division
  • One set of chromosomes is pulled to each end of the cell and the nucleus divides
• Cytokinesis:

  • Cell division
  • Cytoplasm and cell membranes divide 2 daughter cells (clones)
• Before it divides, the cell needs to grow and increase the number of sub-cellular structures (e.g ribosomes and mitochondria)
• Men have Y chromosomes, women only have X ones
• Mitosis is a type of cell division that produces genetically identical cells (clones) and is used for growth, repair (of tissues) and asexual reproduction
• A normal body cell has 4 chromosomes in two pairs

  In the first stage of the cell cycle a copy of each chromosome is made

  The cell divides to form two identical daughter cells, each with a nucleus containing four chromosomes identical to the one in the original parent cell
• Chromosomes are replicated in interphase
• One set of chromosomes is pulled to each end of the cell. the cell uses a special structure called the spindle
• Cytoplasm and cell membrane divide to form two genetically identical cells, so new daughter cells are called clones
• A stem cell is an undifferentiated cell (e.g zygote cell/embryo cells)

  It divides by mitosis to many more cells of the same type

  It can differentiate to form other types of cell
• Cell differentiation is the process of a cell becoming specialised to carry out a particular function

  The cell switched on the genes it needs to use to carry out specific functions

  Other genes that are not needed are switched off

  The cell develops the features it needs to carry out it's specific role
• Stems cells are found in human embryos, in the inner cell mass of blastocyst
• Stem cells are found in human adults in small amounts in most tissues (e.g liver, brain and muscles) and in large amounts in the bone marrow
• In plants, stem cells are found in the meristems (tips of roots and shoots)
• Stem cells are useful in research project because they can differentiate into different types of cells
• An antibody is a protein that's made by white blood cells - they can bind to molecules of complementary shapes (used by immune system to specifically destroy foreign molecules)
• Monoclonal antibodies: Antibodies of one type, produced from a clone of antibody producing white blood cells (lymphocytes)
• A protein on the surface of a cell that antibodies specifically bind to is called an antigen
• Variable region: Different in each type of antibody, antigen binding site, part which joins onto the antigen
• B Lymphocyte: Make antibodies, a type of white blood cell
• Monoclonal: Produced in the lab outside the body, from a clone of cells derived from a single B lymphocyte cell, only recognise one antigen
• Antigen: A foreign protein on the surface of a cell
• Hybridoma: Cell made by fusing a B lymphocyte and a cancer cell, divide very fast (by mitosis), making a clone of cells that make the monoclonal antibodies
• Tumour: Mutant cells - divide rapidly, cancer
• In the reaction zone (of a pregnancy test) The HCG hormone and the monoclonal antibody and the enzyme bind together (only if HCG hormone is present)
• In the test zone (of a pregnancy test) The antigen-hormone complex and fixed antibody bind together. The enzyme is responsible for the colour change of the line
• In the control zone (of a pregnancy test), the fixed antibody binds to the unused antibodies showing the test works + the enzyme causes a colour reaction
• No coloured line on a pregnancy test = faulty test
• Monoclonal antibodies:

  1. An antigen is injected into a mouse
  2. The mouse naturally produces lymphocytes, which produce antibodies specific to the antigen
  3. Spleen cells which produce the lymphocytes are removed during a small operation
  4. The spleen cells are fused with human cancerous white blood cells called myeloma cells to form hybridoma cells which divide rapidly
  5. These hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen