DNA & Protein Synthesis

• Gene

  Short section of DNA that codes for one functional RNA molecule.
• Allele

  Different variants of the same gene e.g. hair colour.
• Loci / Locus

  Location where a gene is found.
• Intron (junk)

  Non-coding sections which are inbetween genes.
• Exon

  Coding region of gene.
• The Genetic Code

  Sequence of bases along its DNA. Each codes for a specific polypeptide and is universal.
• Degenerate

  Multiple codes for one amino acid.
• Genome

  Entire amount of genetic information in an organism.
• Proteome

  Entire set of proteins expressed by an organism.
• (DNA base) triplet

  3 Nitrogenous Bases.
• Codon

  3 mRNA bases
• Anticodon

  3 tRNA bases
• What are the 3 stages of protein synthesis?

  Transcription

  RNA Processing / Splicing

  Translation
• Transcription

  • DNA unwinds at the point where a gene is to be used.
  • The hydrogen bonds between the complementary pairs break
  • The two strands of DNA separate, exposing the bases
  • RNA nucleotides form new hydrogen bonds with the exposed bases on one of the DNA strands via complementary base pairing.
  • An enzyme called RNA polymerase joins the ribose-phosphate backbone of these RNA nucleotides to form a molecule of RNA.
• RNA Processing ( Splicing )

  • Before leaving the nucleus, the pre-mRNA is edited by removing the introns by a spliceosome.
  • The coding sections are then spliced back together to form a functional mRNA
  • The mRNA leaves the nucleus through a nuclear pore.
• Translation Part 1

  • This happens at ribosomes
  • Each ribosome is made up of two subunits & two mRNA codons are attached to the small subunit.
  • The first mRNA codon is always AUG.
  • A tRNA molecule with the complementary anticodon (UAC) forms a hydrogen bond.
  • A second tRNA molecule carrying a different amino acid with a complementary anticodon attaches to the mRNA.
• Translation Part 2

  • A peptide bond forms between the amino acids by condensation reaction, forming a dipeptide, using ATP.
  • The ribosome moves along the mRNA strand so that a third tRNA molecule can attach.
  • The released tRNA is then free to collect another free amino acid from somewhere inside the cell.
• What are the codes for Serine?

  UCU UCC UCA UCG AGU AGC

  
• What are the stop codes?

  UGA UAA UAG