Gene Action and Expression


I.  Introduction

        Protein Structure  :  Polypeptide, and its 3-D conformation.

        Protein sequence:  20 amino acids

        Protein synthesis  === Genetic Transcription  +  Translation

II.  Genetic Transcription

        DNA's information is copied onto mRNA, followed the base pairing rule:  A ---> U, and G--> C

        Triplet code:

        Codon:

III.  The Second Stage in Protein Synthesis  ----  Translation

        Translation:

        Ribosome:

        Transfer RNA  (tRNA) :

        DNA makes RNA make Protein.

Genetic code:

                        Redundancy and life's unity   ----->  Genetic code
 

A Closer Look at Protein Synthesis:

    1.  Protein synthesis begins:  Transcription

            RNA polymerase is responsible for the synthesis of new mRNA strand.

    2.  Messenger RNA processing

        Introns:

        Exons:

    3.  Structure of ribosomes:

    4.  Structure of transfer RNA:

    5.  Steps of Translation:

            mRNA binds to ribosome

            First tRNA arrives

            Polypeptide chain is elongated:  peptide bond formed, A site and P site.

            Termination of the growing chain, termination code:  UAA, UAG, UGA.