Transcription, splicing and translation

• steps of transcription:

  1. DNA is unwound by an enzyme
  2. Hydrogen bonds between complimentary bases are broken by an enzyme
  3. RNA polymerase makes the complimentary RNA
  4. This is called pre-RNA
  5. Splicing- introns are removed, exons are joined together again
  6. Mature RNA leaves the nucleus
• tRNA is clover-shapef
• tRNA is one strand of DNA, but it does have hydrogen bonds
• Steps of translation

  1. mRNA attaches to a ribosome
  2. first tRNA (carrying methionine) forms hydrogen bonds with the start codon on the mRNA
  3. each tRNA has the complementary anticodon to the mRNA codon
  4. second tRNA bonds with the next codon
  5. peptide bond forms between amino acids, requires ATP energy
  6. ribosome moves along mRNA (5' to 3') reading the next codon
  7. third tRNA bonds with complementary codon
  8. first tRNA is released, 2 tRNA fit at any one time
  9. ribosome continues reading mRNA, building polypeptide chain until it reaches a STOP codon
• ribosome reads from 5' to 3'
• only 2 tRNA fit onto the mRNA at any one point
• the first tRNA always carries methionine