1. W HAT DO YOU T HINK ?

3. S TRANGE HUH ?

4. T RANSCRIPTION & T RANSLATION

5. O VERVIEW Transcription Translation DNARNA Protein Characteristics

6. Make Short Notes T RANSCRIPTION & T RANSLATION

7. T RANSCRIPTION  DNA never leaves the nucleus  Proteins are synthesized in the cytoplasm  Therefore a copy of the each gene is made using messenger RNA to carry the message from Nucleus to the Cytoplasm  Transcription Is the synthesis of an RNA molecule with a base pair complementary to a section of DNA

8. T RANSCRIPTION  Usually only a small part of the DNA molecule is transcribed at one time – a section that codes for making one polypeptide is called a GENE  The process starts by the unzipping of the DNA Helix by the enzyme DNA Helicase which break the H + bonds  Free RNA nucleotides slot into place against the DNA strand i.e. A-U, G-C  Temporary H + bonds results to hold the RNA in place and Phosphodiester bonds are created between the RNA nucleotides

9. T RANSCRIPTION  This process is catalyzed by the enzyme RNA polymerase this also ensures that the sequence of amino acids is correct  This elongation of the mRNA continues until the end of the gene or until a STOP codon (ATT, ATC, ACT) is reached  The DNA may zip back up and the mRNA strand exits the nucleus via the nuclear pore into the cytoplasm

10. T RANSLATION  Translation is the process by which the code for making proteins (carried by the mRNA) is used to sequence a polypeptide chain  The sequence of codons is carried on the mRNA  The AUG (Methionine ) codon indicates the start of an amino acid sequence  The mRNA is held in a cleft in the ribosome in the cytoplasm

11. T RANSLATION  A tRNA complementary to the 1 st start codon binds to the mRNA (INITIATION)  Each tRNA carries with it a corresponding amino acid  As the triple codons are read, complementary tRNA molcecules with their amino acids bind to the mRNA  Upon completion, each tRNA molecule breaks free leaving behind its corresponding amino acid

12. T RANSLATION  Peptide bonds form between the amino acids resulting in elongation of the polypeptide  The released tRNA is now available to be reloaded with its complementary amino acid  The polypeptide build up until a STOP codon is reached on the mRNA (TERMINATION)

13. ANSWERS  ACTIVITY 1 TACCGGGTGTACGGGGTG DNA Coding Strand AUGGCCCACAUGCCCCAC mRNA Strand met ala hist met pro hist Polypeptide Sequence N.B. The anticodons on the tRNA are complementary to the codons on the mRNA

14. A NSWERS  Assessment Stage A: Transcription Stage B: Translation Outline the Process occurring at Stage A: It Is the synthesis of an mRNA molecule with a base pair complementary to a section of DNA. Usually only a small part of the DNA molecule is transcribed at one time. The process starts by the unzipping of the DNA Helix by the enzyme DNA Helicase which break the H + bonds. Free RNA nucleotides slot into place against the DNA strand.

15. A NSWERS Assessment cont’d Temporary H + bonds results to hold the RNA in place and Phosphodiester bonds are created between the RNA nucleotides. This process is catalyzed by the enzyme RNA polymerase this also ensures that the sequence of amino acids is correct. This elongation of the mRNA continues until the end of the gene or until a STOP codon (ATT, ATC, ACT) is reached. The DNA may zip back up and the mRNA strand exits the nucleus via the nuclear pore into the cytoplasm

16. THE END Thank You