Genetics

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  • Created by: Sophie
  • Created on: 22-02-14 13:51
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  • Genetics, the Cell Cycle and Differentiation
    • DNA
      • Made of nucleotides
        • A phosphate, a sugar and a base.
          • Base contains nitrogen
      • 2 polynucleotide strands join to form a double helix
        • Sugar-phosphate backbone
        • Specific base pairing
        • Long and coiled up tightly so lots of genetic info fits in a small space in the nucleus
        • Paired structure- for self-replication
        • Stable in cell
    • EUKARYOTIC
      • Linear
        • Associated with proteins
          • DNA wound up around histones, both coiled up to form a chromosome
      • Introns are sections don't code for amino acids
        • Introns removed during protein synthesis
      • DNA also contains sections of multiple repeats
        • e.g CCTTCCTT
    • PROKARYOTES
      • Circular
        • Not
          • Shorter
            • Supercoiled to fit in cell
    • DNA triplet
      • Amino acid
        • Order of amino acids to make a protein
          • Enzymes are proteins, control metabolism and growth etc.
            • Non functional proteins can be the result of gene mutations
              • Mutations are a change in the base sequence
    • Genes can exist in more than one form- allele.
      • Order of bases is slightly different, so they code for slightly different versions of the same thing
    • MEIOSIS
      • Gametes
        • haploid
      • DNA unravels and replicates so there are 2 copied of each chromosome
        • DNA condenses to form a double armed chromosome made from 2 sister chromatids
          • Meiosis I- chromosomes arrange themselves into homologuous pairs
            • H-Pairs separated, halving chromosome number
              • Meiosis II- Pairs of sister chromatids seperate
                • FOUR haploid cells produced
            • As the homologous pairs pair up, the chromatids twist round each other and bits swap over, giving different allele combos
              • Also independent segregation of chromosomes- random chromosomes from parents
    • Genetic diversity
      • Mutations
      • Gene flow- new individuals migrating and reproducing
      • Genetic bottlenecks reduce this as a big reduction in population, reduced alleles
      • The Founder effect- new colony, fewer alleles and more inbreeding
    • The Cell cycle
      • Interpahse, G1, S, G2
        • G1- Protein synthesis
        • S- Replication of DNA
        • G2- Organelles grow and divide, energy stores increased
        • Nucelar division
          • Mitosis or meiosis
          • Cell division
    • Relication- Interphase
      • DNA helicase breaks H-bonds
        • Polynucleotide strands unzip to form single strands
          • Free floating nucleotides join the exposed bases by specific base pairing
            • DNA Polymerase joins the nucleotides on the new strand. New H-bonds between old and new strand
              • Semi conservative as each new DNA molecule has half of the news strands of DNA from the original.
    • Mitosis
      • Clones
      • Repair
      • Interphase
        • Prophase
          • Chromosomes become visible
            • nuclear envelope disappears
          • Metaphase
            • Chromosomes arrange themselves at equator of cell
            • Anaphase
              • Each of the 2 chromatids migrate to opposite poles of the cell pulled by spindle fibres
              • Telophase
                • Nuclear envelope reforms

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