Nucleic Acids

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  • Nucleic Acids
    • Chromosomes
      • The chromosomes are divided into lengths of DNA called Genes
      • Chromosomes are found in homologous pairs, which means they are the same length and have all of the genes in the same position
      • Locus; The position on a pair of homologous chromosomes where a gene is found
      • Allele: One of the different forms of a gene
    • Genes
      • The genes contain all our genetic information and they code for a specific sequence of amino acids that form a particular protein
        • These proteins determine the nature and development of the organism
      • Ribonucleic acid (RNA) is similar in structure to DNA and is also involved in making proteins
      • DNA and RNA are nucleic acids that are found inside the nucleus of cells
        • Deoxyribonucleic acid is the molecule that carries an organism's genetic code
          • The main function of DNA is replication and providing the code for protein synthesis
          • DNA replication ensures the DNA is copied accurately for cell division. When a cell divides, a copy of the DNA is passed to both daughter cells
        • Ribonucleic acid (RNA) is another nucleic acid that is involved in the synthesis of proteins
    • Structure of Nucleotides
      • Consist of a;
        • Pentose sugar
        • A phosphate group
        • An organic nitrogenous base
          • There are 5 different bases;
            • They can be divided into two groups
              • Pyrimidine bases with a single ring structure
                • Cytosine
                • Thymine
                • Uracil
              • Purine bases with a double ring structure
                • Adenine
                • Guanine
            • Adenine, Thymine, Cytosine, and Guanine are found in DNA
            • Adenine, Thymine, Cytosine and Uracil are found in RNA
    • Structure of DNA
      • Single nucleotides join together in a condensation reaction between the phosphate of one nucleotide and the sugar molecule of another forming a nucleic acid with a sugar-phosphate backbone
      • Two antiparallel polynucleotide chains are then joined together by hydrogen bonds forming between pairs of nitrogenous bases
        • The two nucleotide chains then twist together to form a double helix
      • Complementary base pairing
        • Each base can only join with one particular partner, this is called complementary base pairing
        • Purine and pyrimidine bases have different structures so always join together
          • In DNA, Adenine always pairs with thymine (A-T) and guanine always pairs with cytosine (G-C)
            • Pairings depend on the number of H bonds: (A-T) = 2 and (G-C) = 3
          • In RNA, Adenine always pairs with Thymine (A-T) and Guanine always pairs with Uracil (G-U)
          • Base pairings mean that there is always the same proportion of Adenine and Thymine and of Guanine and Cytosine
    • DNA Structure vs Function
      • Job of DNA is to carry genetic information for protein synthesis in cells
        • A DNA molecule is very, very long and coiled up very tightly so a lot of genetic information can fit into a small space in the cell nucleus
      • It's paired structure means it can replicate itself. It is important in cell division so information can be passed on from one generation to the next
    • DNA Structure related to Function
      • Sugar phosphate backbone gives strength to DNA molecules
      • DNA is a long molecule so can store a lot of genetic information
      • The sequence of DNA bases allows for information to be stored
      • The two chains are held together by weak hydrogen bonds and the many weak hydrogen bonds make DNA stable
      • The coiling of DNA protects the weak hydrogen bonds, therefore prevents the code from being corrupted
      • The two chains can separate for transcription and DNA replication


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