genetic mutations

• DNA - double helix held by hydrogen bonds
• DNA - Made up of nucleotides held together by phosphodiester bonds to make a polynucleotide chain
• DNA - Made up of nucleotides held together by phosphodiester bonds
• what sre DNA bases called?

  • adenine
  • cytosine
  • thymine
  • guanine
• how do DNA bases bond

  • A to T
  • G to C
• which two bases are purine?

  • adenine
  • guanine
• transcription -

  1. DNA helicase unzips/unwinds the DNA, hydrogen bonds are broken.
  2. Once the strands are separated, the base sequence on the template strand is used to produce an mRNA molecule.
  3. Free mononucleotides in the nucleoplasm bind to the template strand via complimentary base pairing.
  4. Cytosine binds to Guanine and Uracil binds to Adenine.
  5. RNA polymerase forms phosphodiester bonds between the mononucleotides creating a polynucleotide mRNA molecule.
  6. The completed mRNA disconnects from the DNA and exits the nucleus through a pore in the nuclear envelope to find a ribosome.
• What is a codon?

  A codon is a sequence of 3 bases that code for an amino acid
• Bases are read three at a time i.e. codon by codon.

  A nonoverlapping code means that the same letter is not used for two different codons. In other words, no single base can take part in the formation of more than one codon.
• substitution -

  One base is swapped for another
• insertion -

  a base is inserted causing a frame shift
• deletion -

  a base is deleted causing a frame shift