BY5.1 Protein Synthesis

Genetic Coce

• DNA is the store for the genetic code
• DNA is made up of chromosomes that are divided into genes
• DNA carries information needed to make a particular protein
• the genetic code determines what reactions occur in an organism
• genes control the formation of enzymes and proteins

Nature of the genetic code:

• genetic code determines the primary protein structure
• DNA codes in triplets
• DNA has 4 bases (A,T,G,C)

• the sequence of bases in a DNA chain codes for the sequence of amino acids in a polypeptide chain
• genes are the protion of DNA that codes for a whole polypeptide
• each amino acid is coded for by a codon (3 bases)
• all codons are universal
  • they're exactly the same for all living organisms
• the code is non overlapping
  • each triplet is read separately

RNA:

there are 3 types of RNA:

• messenger RNA (mRNA)
  • formed in transcription
• ribosomal RNA (rRNA)
• transfer RNA (tRNA)

• DNA doesn't leave the nucleus and acts as a template for mRNA
• mRNA carriers the insturctions needed for protein synthesis from the nucelus to the cytoplasm
• ribosomes provide a suitable surface for the attachment of mRNA and the assembly of proteins

Transcription:

• mRNA is copied from a specific area of DNA (the cistron)
• RNA polymerase links to the DNA and DNA unwinds and unzips the relevant region
• only one strand acts as the template
• free RNA nucleotides align themselves to their complementary base pairs…