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Pack 10 - Genetic diversity: mutations, meiosis and adaptions - Coggle…

- - - - -A change in the structure or number of whole chromosomes
      - Polyploidy
        
        Organisms which have 3 or more whole sets of chromosomes. Most eukaryotes are diploid (one set from each parent). Polyploidy is most common in plants and is exploited by humans in improving crop plants
      - Non-disjunction
        
        When individual homologous pairs of chromosomes fail to separate during meiosis. The resulting gametes either have, one more or one fewer, chromosomes. An abnormal number of chromosomes is called an aneuploidy.
        
        In most cases, aneuploidy is not compatible with life - triomies (1 extra chromosome) represents approximately 35% of spontaneous abortions. However, some do survive.
    - - -A change to one or more nucleotide bases, or a change in the sequence of bases within a gene.
      - Substitution
        
        A single nitrogen base substituted for another
        
        May alter primary structure -tertiary - change folding and shape - change function
        
        Sickle Cell Anaemia - substitution mutation causes Haemoglobin to be spiky and stick together and distorts them to sickle shaped in low O2 - this blocks capillaries
        
        Might not cause any change - degenerate coding may mean mutation codes for same amino acid
      - Deletion
        
        Removal of one or more nitrogen base from the sequence
      - Insertion
        
        Addition of one or more nitrogen base into the sequence
      - Frame shift mutation
  - - - Radiation
        
        Chemicals (Nickel, mustard gas, phenol, tar)
        
        Biological agents (some bacteria/viruses)
- - - - 2 daughter cells
        
        Genetically identical
        
        Same number of chromosomes, often diploid
    - - 4 daughter cells
        
        Genetically identical
        
        Half the number of chromosomes, haploid
  - - - Chromosomes condense + become visible, Nuclear membrane disappears, Homologous chromosomes pair up, Chromatids of homologues wrap Crossing over, Portions of chromatids beak off ad re-join (recombination), points where the exchange occur called chiasmata
    - - One of each homologous pair moves to each pole
    - - Homologous pairs of chromosomes line up on equator, Independent segregation
    - - Two daughter cells formed, each containing only one pair of homologous chromosomes
  - - - Chromosomes condense, centrioles move to the poles, nuclear envelope + nucleolus disappear
    - - Centromeres divide, spindle fibres pull chromatids to opposite poles
    - - Chromosomes line up on equator, spindle fibres attach to centromeres and poles
    - - Nuclear membrane reforms, chromosomes decondense
  - - - DNA duplicates
    - - Enzymes and molecules duplicate
    - - Organelles duplicate
- - - - Allele frequency: Divide the number of time an allele is observed by the total number of copies of all alleles
  - - - Selection of a particular characteristic may favour individuals that vary in a direction from mean. Following a change in environment, the mean population will shift in the direction of the individuals with the advantageous allele
    - - In stable environmental conditions, individuals with characteristics sloe to the mean are more likely to survive and pass on the alleles so over time the population spread will reduce and the peak at the mean will increase.