B2 part 1

B2 part 1

1. Cells

   • Animal cells
     • Cell membrane
     • Nucleus
     • Cytoplasm
     • Mitochondria
   • Plant cells
     • Cell membrane
     • Nucleus
     • Cytoplasm
     • Mitochondria
     • Cell wall
     • Central vacuole
     • Chloroplasts
   • Bacteria
     • Chromosomal DNA
     • Cell membrane
     • Some have a flagellum
     • Cell wall
     • Plasmid DNA

2. DNA

   • Breakdown of DNA
     • Cell nucleus
       • Chromosome
         • String of genes
           • A gene is a short piece of DNA
   • Double helix
   • Base Pairs
     • A = adenine
     • T = thymine
     • C = cytosine
     • G = guanine
   • Extracting DNA
     • Fruit mashed up and mixed with salty water and detergent
       • This breaks open the cells and helps release the DNA
         • Protease enzyme is added to filtered mixture, helps to break up proteins
           • Breaking up proteins releases more DNA
             • Ice-cold ethanol is poured into the mixture, makes DNA separate from liquid
   • Discovery
     • Maurice Wilkins and Rosalind Franklin use X-rays to study DNA structure
     • Franklin studied X-ray photographs of DNA to work out how atoms were grouped
     • Watson and Crick interpreted data from other scientists, Franklin's X-ray photos were the final clue
   • Human Genome Project
     • 18 different countries
     • Collaborated to decode the human genome
     • This is the order of bases on all the human chromosomes

3. Genetic engineering

   • Advantages
     • Human insulin using GM is quicker and cheaper
     • Golden rice contains vitamins helping prevent disease
   • Disadvantages
     • A few diabetic people react badly to this insulin
     • Golden rice seeds = expenisive
   • How is it done?
     • A gene is cut out of a human chromosome using enzymes
       • A DNA plasmid is taken out of a bacterium and cut open using enzymes
         • The human insulin gene and the plasmid are mixed together
           • The human insulin gene and the plasmid are stuck together to make a new plasmid
             • The new plasmid with the human insulin gene is put back into a bacterium
               • The bacterium will still make human insulin

4. Mitosis and Meiosis

   • Mitosis
     • Mi-two-sis
       • Makes two cells
     • MiTosis
       • IdenTical cells
     • Diploid means double (two sets of) chromosomes
     • Cell division that happens in body cells
     • The cell that divides is called a parent cell
     • Used in asexual reproduction
     • Used in growth and repairing damaged parts of the body
   • Meiosis and reprduction
     • Fertilisation takes place during sexual reproduction
     • Fertilisation is when a male gamete combines with a female gamete
       • Produces a zygote
     • Sexual reproduction produces variation in offspring
     • Fertilisation
       • Gametes are haploid cells
       • Sperm cell carries chromosomes from mother, egg cell carries mother chromosomes
       • Gametes fuse at fertilisation
       • Zygote is formed - it has one set of chromosomes from each gamete
     • Meiosis
       • Cell division
       • Happens when a diploid cell divides to produce haploid gametes
       • Parent cell is diploid - has two sets of chromosomes
       • Parent cell splits in two twice, four different daughter cells are produced
       • Daughter cells are haploid cells (each has one set of chromosomes)

5. Clones

   • Diploid nucleus is removed from adult body cell
   • Nucleus removed from egg cell, nucleus put in empty body cell
   • Cell simulated with an electric pulse to start mitosis
   • Cell divides and grows as an embryo
   • Embryo placed in uterus of surrogate mother
   • Advantages and disadvantages
     • Animal cloned has good features
     • It is more difficult to clone a mammal than a plant, many attempts needed. Lots of attempts = expensive
     • Cloned mammals may suffer more health problems than usual
     • Any genetic defect in the in parent will be passed on to the offspring

6. Stem cells

   • Embryonic
     • Embryo destroyed when cells removed - some people think embryos have a right to life
     • Body rejects them without use of drugs
     • Produce any type of cell
     • Easy to extract from embryo
   • Adult
     • No embryo destroyed
     • If taken from the person to be treated, the body will not reject it
     • Produce a few types of cells
     • Difficult to find and extract from tissue
   • Replace faulty cell with healthy, so person is well again
   • May produce cancer cells instead of healthy cells

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