1 / 98

Chapter 17 From Gene to Protein

Chapter 17 From Gene to Protein. Question?. How does DNA control a cell? By controlling Protein Synthesis. Proteins are the link between genotype and phenotype. Central Dogma. DNA Transcription RNA Translation Polypeptide. Explanation. DNA - the Genetic code or genotype.

hiero
Download Presentation

Chapter 17 From Gene to Protein

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 17From Gene to Protein

  2. Question? • How does DNA control a cell? • By controlling Protein Synthesis. • Proteins are the link between genotype and phenotype.

  3. Central Dogma DNA Transcription RNA Translation Polypeptide

  4. Explanation • DNA - the Genetic code or genotype. • RNA - the message or instructions. • Polypeptide - the product for the phenotype.

  5. DNA vs RNA DNARNA Sugar – deoxyribose ribose Bases – ATGC AUGC Backbones – 2 1 Size – very large small Use – genetic code varied

  6. Genetic Code • Sequence of DNA bases that describe which Amino Acid to place in what order in a polypeptide. • The genetic code gives the primary protein structure.

  7. Genetic Code • Is based on triplets of bases. • Has redundancy; some AA's have more than 1 code. • Proof - make artificial RNA and see what AAs are used in protein synthesis (early 1960’s).

  8. Codon • A 3-nucleotide “word” in the Genetic Code. • 64 possible codons known.

  9. Codon Dictionary • Start- AUG (Met) • Stop- UAA UAG UGA • 60 codons for the other 19 AAs.

  10. Code Redundancy • Wobble effect: Third base in a codonshows "wobble”. • First two bases are the most important in reading the code and giving the correct AA. The third base often doesn’t matter.

  11. Code Evolution • The genetic code is nearly universal. • Ex: CCG = proline (all life) • Reason - The code must have evolved very early. Life on earth must share a common ancestor.

  12. Reading Frame and Frame Shift • The “reading” of the code is every three bases (Reading Frame) • Ex: the red cat ate the rat • Frame shift – improper groupings of the bases • Ex: thredcatatet her at • The “words” only make sense if “read” in this grouping of three.

  13. Transcription • Process of making RNA from a DNA template.

  14. Transcription Steps 1. RNA Polymerase Binding 2. Initiation 3. Elongation 4. Termination

  15. RNA Polymerase • Enzyme for building RNA from RNA nucleotides.

  16. Binding • Requires that the enzyme find the “proper” place on the DNA to attach and start transcription.

  17. Binding • Is a complicated process • Uses Promoter Regions on the DNA (upstream from the information for the protein) • Requires proteins called Transcription Factors.

  18. TATA Box • Short segment of T,A,T,A • Located 25 nucleotides upstream from the initiation site. • Recognition site for transcription factors to bind to the DNA.

  19. Transcription Factors • Proteins that bind to DNA before RNA Polymerase. • Recognizes TATA box, attaches, and “flags” the spot for RNA Polymerase.

  20. Initiation • Actual unwinding of DNA to start RNA synthesis. • Requires Initiation Factors.

  21. Elongation • RNA Polymerase untwists DNA 1 turn at a time and adds complimentary bases. • Exposes 10 DNA bases for pairing with RNA nucleotides.

  22. Elongation • Enzyme moves 5’ 3’. • Rate is about 60 nucleotides per second.

  23. Comment • Each gene can be read by sequential RNA Polymerases giving several copies of RNA. • Result - several copies of the protein can be made.

  24. Termination • DNA sequence that tells RNA Polymerase to stop. • Ex: AATAAA • RNA Polymerase detaches from DNA after closing the helix.

  25. Final Product • Pre-mRNA • This is a “raw” RNA that will need processing.

  26. Modifications of RNA 1. 5’ Cap 2. Poly-A Tail 3. Splicing

  27. 5' Cap • Modified Guanine nucleotide added to the 5' end. • Protects mRNA from digestive enzymes. • Recognition sign for ribosome attachment.

  28. Poly-A Tail • 150-200 Adenine nucleotides added to the 3' tail • Protects mRNA from digestive enzymes. • Aids in mRNA transport from nucleus.

  29. RNA Splicing • Removal of non-protein coding regions of RNA. • Coding regions are then spliced back together.

  30. Introns • Intervening sequences. • Removed from RNA. • Some contain sequences that regulate gene expression and many affect gene products

  31. Exons • Expressed sequences of RNA. • Translated into AAs.

  32. Introns - Function • Left-over DNA (?) • Way to lengthen genetic message to protect coding regions. • Old virus inserts (?)

  33. Introns- Function • Way to create new proteins with exon shuffling • New combinations of exons= new proteins for evolution

  34. Final RNA Transcript

  35. Translation • Process by which a cell interprets a genetic message and builds a polypeptide.

  36. Materials Required • tRNA • Ribosomes • mRNA

  37. Transfer RNA = tRNA • Made by transcription. • About 80 nucleotides long. • Carries AA for polypeptide synthesis.

  38. Structure of tRNAYou have a diagram of this • Has double stranded regions and 3 loops. • AA attachment site at the 3' end. • 1 loop serves as the Anticodon.

  39. Anticodon • Region of tRNA that base pairs to mRNA codon. • Is a compliment to the mRNA bases, so reads the same as the DNA codon.

  40. Example • DNA - GAC • mRNA - CUG • tRNA anticodon - GAC

  41. Ribosomes • Two subunits made in the nucleolus. • Made of rRNA (60%)and protein (40%). • rRNA is the most abundant type of RNA in a cell.

More Related