Understanding Protein Synthesis: From DNA Transcription to Translation Process

1. PROTEIN SYNTHESIS

2. DNA  TRANSCRIPTION  RNA  TRANSLATION  PROTEIN

3. Gene DNA Protein Trait

4. Phosphate Group O O=P-O O Nitrogenous base (A, U,G, C ) 5 CH2 O N Sugar (ribose) C1 C4 C3 C2 RNA

5. RNA • Function: obtain information from DNA & synthesizes proteins

6. 3 differences from DNA • Single strand instead of double strand • Ribose instead of deoxyribose • Uracil instead of thymine

7. Nucleotidestructure of RNA

8. 3 types of RNA • Messenger RNA(mRNA)- copies information from DNA for protein synthesis Codon-3 base pairs that code for a single amino acid. codon

9. 3 types of RNA 2.Transfer RNA(tRNA)- carries amino acids to the ribosomes for protein synthesis Anticodon-a sequence of 3 bases that are complementary base pairs to a codon in the mRNA

10. 3 types of RNA 3. Ribosomal RNA(rRNA)- where the aa’s are put together to make a protein

11. Amino Acids • Amino acids-the building blocks of protein • At least one kind of tRNA is present for each of the 20 amino acids used in proteinsynthesis.

12. Transcription - mRNA is made from DNA & goes to the ribosome Translation- Proteins are made from the message on the mRNA

13. Transcription • In order for cells to make proteins, the DNA code must be transcribed (copied) to mRNA. • The mRNA carries the code from the nucleus to the ribosomes.

14. TRANSCRIPTION PRACTICE • AGG CCT GCT  TEMPLATE • TCC GGA CGA  NON- TEMPLATE • mRNA (CODONS) • UCC GGA CGA

15. TGG CAG CTA  DNA • ACC GUC GAU TRANSCRIPTION (mRNA)

16. Translation • At the ribosome, amino acids (AA) are linked together to form specific proteins. • The amino acid sequence is directed by the mRNA molecule. Amino acids ribosome

17. Make A Protein • DNA sequence ATG AAA AAC AAG GTA TAG • mRNA sequence UAC UUU UUG UUC CAU AUC

18. Make mRNA • mRNA sequence UAC UUU UUG UUC CAU AUC • tRNA sequence AUG AAA AAC AAG GUA UAG

20. Make mRNA • mRNA sequence UAC UUU UUG UUC CAU AUC Amino Acid sequence TYR PHE LEU PHE HIS ILE

21. Early evidence indicating most genes specify the structure of proteins • Garrod’s work on inborn errors of metabolism in early 1900s • Beadle and Tatum’s work with Neurospora mutants in the 1940s

22. An“inborn errorof metabolism”

23. Information flow from DNA to protein • Transcription • RNA molecule complementary to the template DNA strand synthesized • Translation • Polypeptide chain specified by messenger RNA (mRNA) is synthesized

24. Overview of transcription and translation

25. Synthesis of mRNA

26. Three representations of a tRNA molecule

27. Ribosomestructure

28. Initiation of translation in bacteria

29. Elongation cycle in translation

30. Termination of translation

31. Coupled transcription and translation in bacteria • Unlike eukaryotic cells, in bacterial cells translation and transcription coupled • Translation of the bacterial mRNA molecule usually begins before the 3´ end of the transcript is completed

32. Coupled transcription and transla-tion in bacteria

33. Retroviruses • Flow of genetic information is reversed by reverse transcriptase • Enzyme associated with retroviruses • Retroviruses synthesize DNA from an RNA template • Example of retrovirus is HIV-1, AIDS virus

34. Infection cycle of an RNA tumor virus

35. Mutations • Base substitution mutations • Often result from errors in base pairing during replication • Missense mutations • Nonsense mutations • Frameshift mutations • One or two nucleotide pairs are inserted into or deleted from the molecule

36. Some mutations involve larger DNA segments • Due to change in chromosome structure • Wide range of effects as they involve many genes • DNA sequences that “jump” into the middle of a gene • Known as transposons or transposable genetic elements • Most are retrotransposons

37. Mutations

38. Mutations • What causes mutations? • Can occur spontaneously • Can be caused by a mutagen • Mutagen:An agent, such as a chemical, ultraviolet light, or a radioactive element, that can induce or increase the frequency of mutation in an organism.

39. Mutations • Some mutations can: • Have little to no effect • Be beneficial (produce organisms that are better suited to their environments) • Be deleterious (harmful)

40. Mutations • Types of mutations • Point Mutations or Substitutions: causes the replacement of a single base nucleotide with another nucleotide • Missense- code for a different amino acid • Nonsense- code for a stop, which can shorten the protein • Silent- code for the same amino acid (AA)

42. THE FAT CAT ATE THE RAT • THE FAC CAT ATE THE RAT

44. Mutations • Example: Sickle Cell Anemia

45. Mutations • Types of mutations • Frame Shift Mutations: the number of nucleotides inserted or deleted is not a multiple of three, so that every codon beyond the point of insertion or deletion is read incorrectly during translation. • Ex.: Crohn’s disease

46. THE FAT CAT ATE THE RAT • THE FAC ATA TET HER AT • THE FATT CAT ATE THE RAT • THE FAT TCA TAT ETH ERA T

47. Mutations

48. Mutations • Types of mutations • Chromosomal Inversions: an entire section of DNA is reversed. • Ex.: hemophilia, a bleeding disorder

50. DNA Repair • A complex system of enzymes, active in the G2 stage of interphase, serves as a back up to repair damaged DNA before it is dispersed into new cells during mitosis.