Protein Synthesis

• The order of bases in a section of DNA decides the order of amino acids which fold up giving a protein with a specific shape e.g. enzymes
• Protein Synthesis:

  1 - Transcription

  • RNA polymerase binds to a non-coding part of DNA in front of a gene
  • DNA unzips and the RNA polymerase produces a complementary mRNA strand from the coding DNA - template strand
  • mRNA molecule leaves the nucleus and into the cytoplasm

  2 - Translation

  • Ribosome binds to mRNA and is brought specific amino acids by tRNA (transfer) that match the order of the base triplet - codon
  • Amino acids join together and form a polypeptide
• In mRNA, the base pair Uracil (U) is used instead of Thymine (T).
• The base pairs in DNA are T + A and G +C.
• Genetic variants (a mutation in a gene) in the non-coding part of DNA can affect the phenotype by altering the ability of RNA polymerase to bind to the DNA. This affects how much mRNA is transcribed and how much protein is produced.
• Genetic variants in the coding part of DNA can affect the phenotype by altering the sequence of amino acids changing its shape and therefore its activity of the protein produced.