DNA, genes and chromosomes

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  • DNA, genes and chromosomes
    • prokaryotic cells
      • no nucleus
      • DNA is short, circular and not associated with proteins
      • DNA isn't around histones - it condenses to ft in the cell by super coiling
    • eukaryotic cells
      • DNA in the nucleus
      • DNA is linear, long and is associated with proteins called histones
        • DNA and histones form a chromosome
      • mitochondria dn chloroplasts contain DNA without histones
      • most of the DNA doesn't code for proteins
        • exon = coding sequence within a gene
        • intron = non-coding sequence within a gene
        • larger regions have repeats of bases between genes
    • genes
      • a base sequence of DNA
        • codes for amino acid sequence of a polypeptide , or a functional RNA
      • Found at a specific position on a DNA molecule
        • locus
      • amino acid sequence
        • primary structure of a protein
        • different polypeptides have different order, number of amino acids
          • the order of bases determine the amino acid
            • triplet code
          • to make a polypeptide DNA is copied into mRNA
      • functional RNA
        • RNA molecules (other than mRNA) which perform special tasks during photosynthesis
      • alleles are different versions of the same gene
        • the order of bases in each alley is slightly different, so they code for slightly different versions of the same polypeptide
      • genetic code
        • degenerate
          • multiple triplets code for 1 amino acid
        • universal
          • each triplet codes for the same amino acid in all organisms
        • non-overlapping
          • base triplets don't share bases

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