Protein Synthesis

1. Protein Synthesis “From code into Flesh & Blood”

2. Why RNA Synthesis is “easier” • Whole DNA molecule not unwound:  no single-stranded binding proteins  no topoisomerase • RNA polymerse, not DNA polymerase  no primer needed  still 5’ 3’ (but no lagging strand, no Okazaki fragments)

3. Protein Synthesis: Prok vs. Euk • Location • mRNA processing

4. Fig. 17-3a-1 DNA TRANSCRIPTION mRNA (a) Bacterial cell

5. Fig. 17-3a-2 DNA TRANSCRIPTION mRNA Ribosome TRANSLATION Polypeptide (a) Bacterial cell

6. Fig. 17-3b-1 Nuclear envelope DNA TRANSCRIPTION Pre-mRNA (b) Eukaryotic cell

7. Fig. 17-3b-2 Nuclear envelope DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA (b) Eukaryotic cell

8. Fig. 17-3b-3 Nuclear envelope DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA TRANSLATION Ribosome Polypeptide (b) Eukaryotic cell

9. mRNA “processing” • “Head” end – “5’ cap” = modified guanine • “Tail” end – 3’ “poly-A’ tail • “splicing” of message!?! • Cut out “introns” • “exons” are expressed

10. Eukaryotic cells modify RNA after transcription

11. Three Types of RNA • mRNA • tRNA • rRNA • All single stranded • All transcribed from DNA “genes” • Only mRNA translated into protein

12. Fig. 17-14a 3 Amino acid attachment site 5 Hydrogen bonds Anticodon (a) Two-dimensional structure

13. Fig. 17-14b Amino acid attachment site 5 3 Hydrogen bonds 5 3 Anticodon Anticodon (c) Symbol used in this book (b) Three-dimensional structure