Biology

• Mitosis


  Cell division that produces two identical daughter cells
• Mitosis


  1. Interphase

  2. Prophase

  3. Chromosomes start to become visible

  4. Nuclear membrane breaks down

  5. Each chromosome has 2 chromatids
• Mitosis


  • Produces 2 identical daughter cells
  • If parent cells are diploid, daughter cells are diploid
• Mitosis takes place in 5 stages
• Magnification


  The ratio of the size of the image to the size of the real object
• Magnification


  • Measured in x by 1000
  • To get answer in pm
  • Relates to object size
• Calculating magnification


  1. Magnification of eye piece

  2. Magnification of objective

  3. Multiply to get total magnification
• Magnification = Magnification of eye piece x Magnification of objective
• Meiosis


  The process where a diploid parent cell produces four haploid daughter cells
• Parent cell


  • Diploid
  • Has 2 sets of chromosomes
• Meiosis


  1. Parent cell has 2 sets of chromosomes

  2. Each chromosome is copied

  3. Parent cell divides twice to produce 4 daughter cells

  4. Each daughter cell has 1 set of chromosomes (haploid)
• Diploid parent cell produces 4 haploid daughter cells
• Genetic engineering


  1. DNA cut with restriction enzymes

  2. Restriction enzymes make staggered cuts across DNA

  3. Leaving a few unpaired bases called sticky ends
• Plasmid modification


  1. Plasmids are cut using restriction enzymes

  2. Leaving sticky ends to match the unpaired bases
• Genetic engeneering

  1. Pieces of DNA containing the desired characteristics are mixed with the plasmids

  2. Bases in sticky ends pair up

  3. Ligase is added linking the DNA back together

  4. Plasmids are inserted into bacteria
• Selective breeding


  Certain characteristics desired are chosen to breed, so their offspring will inherit these desired characteristics
• Selective breeding


  • Advantages: faster growth, better flavour, increase in yield
  • Disadvantages: physical problems, costs veterinary bills, bad for animal welfare, wasted embryos
• Selective breeding is done to produce offspring with desired characteristics
• Natural selection


  • Some individuals are able to survive their environment and produce healthier offspring
• Darwin's theory


  1. Over production leads to a struggle for existence for offspring

  2. Some are healthier

  3. Some not. Therefore these won't reproduce
• Gene

  Short piece of DNA that codes for a specific protein
• DNA


  • Coiled molecule formed from 2 strands in a double helix
  • These strands are joined by pairs of bases
  • Complementary pairs: AT GC
  • They are joined by weak hydrogen bonds
• Zygote


  • Diploid cell formed when gametes fuse at fertilisation
  • Each zygote inherits different alleles of their genes from their parents
• This produces variation in inherited characteristics
• Chromosome


  Molecule made up of many coiled sections of DNA
• Alleles


  Different versions of the same gene
• Phenotype


  What the individual looks like
• Genotype


  The genes of an individual
• Embryonic stem cells


  • Cells from an embryo
  • Embryo is destroyed when cells are removed
  • Some people are against this
• Adult stem cells


  • Can only produce a few cell types
  • Can produce any type of cell
  • Easy to extract
  • No embryo is destroyed
• Adult stem cells do not have an ethical issue
• Sensory neurons


  • Carry Impulses to central nervous system
• Stem cells


  Unspecialised cells that can divide to produce specialised cells
• Embryonic stem cells


  • Divide to produce specialised cells
  • Once cells have differentiated, they cannot divide into other types of cell
• Types of stem cells

  • Embryonic
  • Adult
• Embryonic stem cells


  • Can replace or repair brain cells to treat Parkinson's disease
  • Can replace damaged cells in the retina of the eye to treat some blindness
• Adult stem cells


  • Can be used to treat leukaemia
  • Can be used to grow new tissues genetically matched to the individual
• Diffusion


  Movement of particles across a partially permeable membrane from a high concentration to low concentration, down the concentration gradient
• Diffusion


  • Lungs
• osmosis

  Movement of water in and out of cells through a partially permeable membrane