Protein Synthesis: Part 1 (Transcription)

1. Protein Synthesis: Part 1 (Transcription) Ch 11

2. Protein Synthesis means Synthesizing Proteins or “MAKING” PROTEINS

3. The GOAL is to: learn how proteins are made.

4. Protein Synthesis can be broken down into two stages: • Transcription • Translation

5. 1st PROCESS 2nd PROCESS TRANSCRIPTION TRANSLATION DNA mRNA Proteins 1 2 3

6. Transcription Reads and copies a section of DNA (AKA gene) and converts it into mRNA (A gene codes for a protein)

7. Let’s compare DNA and RNA

8. DNA RNA Sugar = ribose Sugar = deoxyribose Single strand Double helix (2 strands)

9. DNA RNA Location: Nucleus & cytoplasm Location: nucleus Bases: A, C, G, T Bases: A, C, G, U (Uracil)

10. DNA RNA Function: many functions, all used to assemble proteins Function: simply stores genetic info (instructions to make proteins)

11. Three types of RNA • MESSENGER RNA (mRNA) • TRANSFER RNA (tRNA) • RIBOSOMAL RNA (rRNA)

12. MESSENGER RNA • “mRNA” • single strand • contains genetic info • is transported out of nucleus

13. TRANSFER RNA • “tRNA” • single strand • folded like a hairpin • binds specific amino acids

14. RIBOSOMAL RNA • “rRNA” • single strand • found in ribosomes • ribosomes are made up two pieces of rRNA

15. Let’s look at TRANSCRIPTION “The first process”

16. DOUBLE HELIX SPREADS APART RNA POLYMERASE copies the gene by attaching RNA nucleotides The product is called mRNA mRNA

17. Here the DNA is split open and a mRNA strand is being made

18. Here the DNA is split open and a mRNA strand is being made

19. NOTICE: RNA POLYMERASE ADDS ON RNA NUCLEOTIDES TO MAKE mRNA

20. Then the newly constructed mRNA undergoes “processing” mRNA mRNA The mRNA then leaves the nucleus to enter the next process “translation”

21. DNA RNA DNA 5’ 3’ A U G A C U A U A G A T G A C T A T A G T A C T G A T A T C “start” sequence (Signals where to begin) “terminator” sequence (where to end) 5’ 3’

22. RNA processing includes • cutting out meaningless DNA (aka introns) • Adding a cap on the tip (aka GTP cap) • Adding on A-A-A-A on the end (aka Poly-A tail)

23. Intron Intron Intron + Introns contain meaningless DNA = Only the important, USEFUL DNA

24. GTP A-A-A mRNA Add on a GTP cap Tack on a poly-A tail You are finished processing the mRNA. It can now leave the nucleus.

26. Describe what is happening here and who is involved

27. Translation • The process of converting the mRNA codons into a sequence of amino acids to build a protein. • A codon is a group of three nucleotides. Each codon codes for one amino acid.

28. Translation – using mRNA to bring the correct tRNA anticodon, with an amino acid attached. Occurs at the ribosome. .

29. Translation Sequence • A ribosome attaches to the “start” of the mRNA. The codon “AUG” signals the start. • The tRNA having the anticodon “UAC” will bring the first amino acid to the ribosome to begin the formation of the protein. • The ribosome slides to the next codon on the mRNA. The complementary tRNA anticodon brings the second amino acid to the protein strand.

30. This process continues until the ribosome reaches a “stop” signal. • Stop codons on mRNA are • UAA • UAG • UGA A Protein has been made!

31. Mistakes Happen – Mutations! A point mutation occurs when a single base pair is mismatched. Ex. THE DOG BIT THE CAT THE DOG BIT THE CAR A frameshift mutation occurs when a single base is added or deleted. Ex. THE DOG BIT THE CAT THE OGB ITT HEC AT (the D was deleted)

32. Which do you think would be more harmful? Why?