KEY FACTS: PROTEIN SYNTHESIS (TRANSCRIPTION AND TRANSLATION)

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STEP ONE TRANSCRIPTION: 

THE PLAYERS: DNA, RNA nucleotides, mRNA and RNA polymerase

  • The DNA of a gene is not used to make polypeptides in the nucleus. Instead, RNA copies of the gene's code are made.

 

  • One strand of the gene's DNA is used to make many copies of messenger RNA, which have a matching code. This process is transcription.

 

  • The base sequence of mRNA is complementary to the coding strand of DNA. Except of course U instead of T

 

  • RNA polymerase joins the RNA nucleotide to each other

 

 

 

INTERLUDE:  The mRNA passes out of the nucleus and attaches to ribosomes on the rough endoplasmic reticulum.

 

STEP TWO TRANSLATION: 

THE PLAYERS:  mRNA, ribosomes, tRNA and amino acids

 

  • The rough endoplasmic reticulum has a supply of transfer RNA molecules that have specific amino acids attached. The tRNA molecules have anticodons that bind to the corresponding mRNA codon.

  • As the mRNA moves through a ribosome, the amino acids carried by the tRNA are combined in the correct sequence to form the polypeptide. This process is translation.
  • The polypeptides formed can then be used to make a specific protein, which may be, for example, an enzyme, a membrane protein or a structural protein.