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Biology - Paper 2 (Inheritance, Variation and Evolution (DNA (Mutations,…

- - - - DNA is found in long structures called chromosomes. Chromosomes usually come in pairs and humans have 46 (23 pairs).
        
        A gene codes for a specific protein using a particular sequence of amino acids.
    - - DNA is made up of lots of repeating units called nucleotides. Each nucleotide consists of one sugar molecule, one phosphate molecule and one base.
        
        The sugar and phosphate alternate to form a sugar phosphate backbone. There are 4 bases in DNA, A, T, C and G. A always binds with T and C always binds with G.
    - - The DNA is too large to leave the nucleus
        
        mRNA is used to deliver specific sections of DNA to the ribosomes for protein synthesis.
        
        It copies the length of DNA that is needed for a singular protein
        
        The mRNA then carries the copied DNA to the ribosome where it is read and the correct amino acids are assembled in the right order in a chain to make a protein.
    - - Mutations occur randomly, sometimes they have no effect, sometimes they have a positive effect and sometimes they have a negative effect. Due to darwins theory of natural selection, those in a species who have positive mutations have an advantage over the rest of the species and so are more likely to live and pass on the mutation to offspring.
      - Types of
        Mutations
        
        Isertion - This is when a base is inserted into the sequence. This can have a knock on effect meaning multiple amino acids are changed.
        
        Deletion - This is when a base is deleted from the sequence. This can have a knock on effect meaning more than one amino acid is effected.
        
        Substitution - This is when a base is changed to a different base. This only affects a singular amino acid so it is less likely to be detrimental to the proteins function.
  - - - Advantages
        
        Provides variation
        
        Increases the chance of a species surviving a change inthe environment
        Disadvantages
        
        Two parents are required
        
        Less energy efficient
        
        Slower
    - - Advantages
        
        Only one parent is required
        
        Less energy required
        
        Faster
        
        More offspring can be produced quicker in favourable conditions
        Disadvantages
        
        Lack of genetic variation
        
        More likely to be wiped out in a change to the environment
  - - - Cystic
        Fibrosis
        
        Cystic Fibrosis is a genetic disorder of the cell membranes. It results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas. It is caused by a recessive gene
      - Polydactyly
        
        Polydactyly is a genetic disorder where a baby is born with extra fingers or toes. It is caused by a dominant gene
      - Embryonic
        Screening
        
        A cell can be taken form an embryo and it's DNA can be analysed. This means it can be screened for genetic disorders and if an embryo is tested as positive for a genetic disorder, it can be aborted in favour of another healthy embryo.
        
        Advantages
        
        Helps people stop suffering
        
        Treating disorders costs a lot of money
        
        There are strict laws in place to stop it going too far, at the minute parents can't even decide the sex of their child.
        Disadvantages
        
        Implies that people with genetic disorders are undesirable, increasing prejudice.
        
        It may progress to parents picking desirable characteristics like blue eyes blond hair.
        
        It's expensive
- - - - Glycogen
        This is what the liver converts glucose into, it acts as a storage for when glucose falls too low.
      - Glucagon
        This is secreted by the pancreas when glucose levels are too low. It causes glycogen to convert back into glucose
      - Insulin
        This is secreted by the pancreas when glucose levels are too high. It causes the liver to convert glucose into glycogen
    - - Type 1
        
        When the pancreas produces little or no insulin. Treatments are insulin therapy, the injection of exterior insulin. Usually manifests in earlier life.
      - Type 2
        
        When a person becomes resistant to their own insulin. Insulin is still produced but it is not effective. This can be reversed through a lifestyle change in terms of diet and exercise.
  - - - Urea
        
        Proteins are too large a molecule to store, so through the proces of Deamination in the liver they are converted into fats and carbs. A waste product of this is ammonia which is toxic so it is converted to urea so it can be safely removed from the blood.
      - Ions
        
        Ions are used to control the rate of osmosis in cells, so if ions are in excess they must be removed in urine.
      - Water
        
        This is the bodies mechanism for balancing the amount of water in our body