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1. FROM GENE TO PROTEIN Susheel Dwivedi –www.bioguruindia.com Proteins make the Organism

3. The Dictionary of The Genetic Code

6. Transcription Initiation

9. mRNA Elongation

11. mRNA SPLICING

12. Spliceosomes

19. The Nucleolus – Home of Ribosome Assembly

21. Transfer RNA (tRNA)

22. Aminoacyl-tRNA Synthatase An enzyme that adds amino acids to the 3’ end of the free tRNA

23. Translation Initiation E, P and A sites Each ribosome has a binding site for mRNA and three binding sites for tRNA molecules. The P site holds the tRNA carrying the growing polypeptide chain. The A site carries the tRNA with the next amino acid. Discharged tRNAs leave the ribosome at the E site

24. Polypeptide Elongation

25. Polypeptide Elongation, cont’d.

26. Termination When the stop codon enters the ribosome, a protein called a release factor enters the A site and hydrolyzes the bond between the tRNA in the P site and the last amino acid of the polypeptide chain. This frees the polypeptide and breaks up the ribosomal subunits.

28. The Dictionary of The Genetic Code

33. Some polypeptides have an ER signal sequence. The signal sequence is recognized by a Recognition Particle, or SRP. This is then bound to a receptor. This complex guides the protein through a channel like region. It also consists of a docking site for the ribosome. Bound versus Free Ribosomes and the role of the Endoplasmic Reticulum

36. Substitutions - Missense mutations EXAMPLE: sickle-cell disease The replacement of A by T at the 17th nucleotide of the gene for the beta chain of hemoglobin changes the codon GAG (for glutamic acid) to GTG (which encodes valine). Thus the 6th amino acid in the chain becomes valine instead of glutamic acid. A single base, say an A, becomes replaced by another. Single base substitutions are also called point mutations.

39. Insertions and Deletions Extra base pairs may be added (insertions) or removed (deletions) from the DNA of a gene. This usually causes a shift in the reading frame and changes the amino acid sequence of the protein from that point onward. Frameshifts often create new STOP codons and thus generate nonsense mutations. Perhaps that is just as well as the protein would probably be too garbled anyway to be useful to the cell.

42. Thymine Dimers

45. The Wobble Rules Wobble Rules: Read as 5' position in anticodon pairs with 3' position in codon: G pairs with C or U; C pairs with G; A pairs with U; U pairs with A or G; I pairs with A, U, or C Note that the anticodon position in the tRNA can also have the base inosine (I), a purine that is not present in the messenger RNA (codon)

48. Euchromatin vs. Heterochromatin

55. Polytene chomosome from the salivary gland of Drosophila melanogaster (stained)

56. Get more Protein With Your Carbohydrates THE END Susheel Dwivedi –www.bioguruindia.com