DNA Replication and the Genetic Code 3.9

DNA Replication and the Genetic Code 3.9

1. Semi conservative replication

   • DNA undergoes replication
     • DNA helicase causes two strands to seperate by breaking the polynucleotide strands. The helix unzips.
       • Each original strand acts as a template and free nucleotides are attracted to the bases
         • Nucleotides and bases are joined together by DNA polymerase forming the sugar phosphate backbone. Hydrogen bonds form between bases
           • 2 identical strands form. All nucleotides form a complete polynucleotide
   • Proof
     • Stahl and meselsohn experimented in 1958

2. Genetic Code

   • Triplet code - three nucleotides make up a triplet code. Also known as a codon
   • Universal
   • Scientists understood that proteins were made up of amino acids
   • Scientists understood that DNA must code for proteins and therefore carry instuctions
   • Scientists determined that DNA passed genetic information on
   • Eventually, they discovered DNA must code for a sequence of amino acids - the genetic code

3. Degenerate Code

   • There are 4 different bases meaning there are 64 possible codons
   • There is a starting codon and an ending codon
   • This prevents overlap meaning its non overlapping