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Module 6 - Coggle Diagram

- - - - Nitrogenous bases are divided into two groups: pyrimidines and purines.
        
        Pyrimidines: Smaller bases, contain single carbon ring structures - thymine (T) and cytosine (C.)
        
        DNA - Double helix structure: DNA consists of two nucleotide strands, coiled together to form a helix, known as a double helix. These two strands are connected by hydrogen bonds between complementary bases (thymine and adenine, guanine and cytosine.) The double helix is known as antiparallel as the strands run in opposite directions. One strand consists of connections between the 3rd carbon of the pentose sugar, and the phosphate group attached at the 5th carbon. These connections are known as phosphodiester bonds.
        
        Purines: Larger bases, containing double carbon ring structures - adenine (A) and guanine (G)
  - - - The two strands of a DNA helix are separated by the DNA helicase enzyme.
        
        Free moving activated nucleotides are attracted to their respective complementary bases on each strand.
        
        The enzyme DNA polymerase join together aligned nucleotide bases until eventually forming a polynucleotide chain consisting of one new and one original nucleotide strand. In turn, a section of DNA will helix produce two new helices, each with an one original strand.
    - - DNA must code for a sequence of amino acids which then go onto to form complex structures. DNA's informing of amino acid sequences is known as the genetic code.
        
        Triplet code and codon
        
        Every three nucleotide bases make up a triplet code known as a codon, which in turn codes for an amino acid.
        
        Gene
        
        A section of DNA that contains the complete sequence of bases or codons for an entire protein.
        
        Each set of bases that form a triplet code contains a start codon at the beginning of the sequence that signals it's start, and one of three potential "stop codons" that signal the end of the sequence. The stop codon does not code for any amino acids.
        
        Having a single start codon ensures that that the triplets of bases are read "in frame" and that the sequence is read from base 1 not 2 or 3, preventing genetic code from over - lapping.
        
        Genetic code is known as a degenerate code, meaning there are only 20 amino acids, but 64 available base triplets, which in turn means several codons can code for the same amino acid.