Protein Synthesis: Transcription and Translation

1. Objectives I know what a gene is I can describe the process of protein synthesis I can describe the functions of the three types of RNA I can predict the protein that will be made from a strand of DNA

2. Protein Structure

3. GENES

6. DNA - BLUEPRINTS NUCLEUS DNA HAS TO SEND A MESSAGE HOW IS DNA GOING TO TELL THE RIBOSOMES WHAT TO MAKE? RIBOSOMES CYTOPLASM MAKES PROTEINS

7. AA AA AA AA Protein Synthesis TRANSCRIPTION TRANSLATION “WRITE THE MESSAGE” “DECODE THE MESSAGE” mRNA PROTEIN DNA

8. NUCLEUS AA AA AA AA DNA REPLICATION & TRANSCRIPTION TRANSCRIPTION TRANSLATION CYTOPLASM RIBOSOMES

9. RNA – THE MESSAGE A U C G U

10. T A U T A C G C G T A U G C A DNA RNA R D

11. RNA • Ribonucleic Acid • Single stranded • Has ribose sugar • Has Uracil instead of Thymine • Bonding Pattern • A - U • C - G

12. 3 types of RNA • mRNA – messenger RNA – carries DNA “message” from the nucleus to the rest of the cell • tRNA – transfer RNA – brings or “transfers” amino acids from the cytoplasm to the ribosomes to assemble proteins • rRNA – ribosomal RNA – helps make up ribosomes

13. Making Proteins: 2 steps Transcription = re-writing the instructions from the language of DNA to the language of RNA • WHY? Because DNA is too large to leave the nucleus, but mRNA can slip out through the nuclear pores Translation = de-coding the message (mRNA CODES for Amino Acids)

14. Transcription – making of mRNA • Copy part of DNA into complementary RNA strand “Writing of RNA using DNA” • RNA polymerase – enzyme that binds to DNA to use as template and assemble RNA nucleotides • Binds to region of DNA called the ‘promoter’ which tells the enzyme where to start • RNA polymerase releases DNA strand when RNA strand is complete • mRNA will then travel into cytoplasm

16. U C G U A DNA is TRANSCRIBED into mRNA D R A D R G D R C D A R D R T

17. Transcribe this DNA sequence CATGACTAG GUACUGAUC

18. AA AA AA AA Protein Synthesis TRANSCRIPTION TRANSLATION “WRITE THE MESSAGE” “DECODE THE MESSAGE” mRNA PROTEIN DNA

20. NUCLEUS AA AA AA AA DNA REPLICATION & TRANSCRIPTION TRANSCRIPTION TRANSLATION CYTOPLASM RIBOSOMES

21. TRANSLATION • The process of translating or decoding the DNA message (mRNA) into amino acid chains (proteins) • tRNA • tRNA have 3 bases on them called an anticodon which pairs with the codon of the mRNA • Each tRNA adds one amino acid that it has brought from the cytoplasm making the protein chain longer

22. U G C ANTICODON tRNA – cloverleaf shape

23. AA AA AA AA U A C G U A A U G A C U RIBOSOMES tRNA A U G C A U U A C U G A mRNA CODON

24. Steps of Protein Synthesis • mRNA leaves nucleus and attaches to ribosomes • tRNA with the anticodon UAC attaches to the mRNA start codon AUG to begin protein chain with amino acid methionine • Additional tRNA’s add other amino acids to the protein chain connecting them with peptide bonds • Protein synthesis continues until it reaches a stop codon (UGA, UAA, UAG)

25. Genetic Code • Proteins are built from different combinations of 20 amino acids • AA sequence is determined by sequence of bases in mRNA • Each 3 base codon “codes” for a different amino acid • 64 possible codons • 61 code for 20 amino acids • 3 are “Stop” codons

26. How do we know what Amino Acid to add? USE THE mRNA CODE TO TRANSLATEINTO AMINO ACID’S mRNA – 1) AUG 2) CAU 3) UAC 4) UGA

27. MET HIS MET TYR HIS MET MET HIS TYR U A C G U A A U G A C U RIBOSOMES tRNA A U G C A U U A C U G A mRNA CODON

28. PRACTICE • DNA : T A C G A C G T A A A A A C T • mRNA: ? • tRNA: ? • Amino Acid Sequence: ?

29. PRACTICE • DNA : T A C - G A C - G T A - A AA - A C T • mRNA: A U G - C U G - C A U - U UU - U G A • tRNA: U A C - G A C - G U A - A AA - A C U • AA Seq: MET - LEU - HIS - PHE

30. T T G T G DNA Replication A A C A C

31. U C G U A DNA TRANSCRIPTION D R A D R G D R C D A R D R T DNA mRNA

32. NUCLEUS DNA REPLICATION & TRANSCRIPTION TRANSCRIPTION AA AA AA AA RIBOSOMES CYTOPLASM TRANSLATION

33. PRACTICE • DNA : TAT – CGC – AGC • mRNA: AUA – GCG - UCG • Amino Acid Sequence: Ile - Ala - Ser