RNA and Protein Synthesis

1. RNA and Protein Synthesis Chapter 13 (Pgs 360-389 Miller and Levine Biology text) http://www.youtube.com/watch?v=suN-sV0cT6c

2. Where have we seen DNA being replicated? MITOSIS AND MEIOSIS

3. Proteins are molecules that are necessary for virtually every activity in your body. Some of the Biological Functions of Proteins include:

4. Genotype  Phenotype DNA mRNA tRNA PROTEIN Transcription Translation

5. How are DNA and RNA different? • DNA… • Nucleotides = deoxyribose sugar • Double helix structure • Stays inside nucleus • RNA… • Nuleotides = ribose sugar • Single-strand structure • Located both inside and outside of nucleus • Uracil instead of thymine

6. How are DNA and RNA different?

7. A Closer Look at RNA: • Contains ribose sugar instead of deoxyribose sugar • Single stranded • The nucleotide uracil replaces thymine

8. 3 Types of RNA • Messenger RNA = mRNA • -Carries genetic coded message sequence from DNA, in the nucleus to the ribosome in the cytoplasm. • Ribosomal RNA = rRNA • - One of components of the • ribosome, rRNA associates with protein to form the ribosome. There are 1000’s of ribosomes/cell. • -Ribosomal RNA (rRNA) is part of the ribosome. rRNA consists of two subunits that are made up of several ribosomal RNA. Proteins are assembled on the ribosomes. • Transfer RNA = tRNA • - Transfer RNA (tRNA) transfers each amino acid to the ribosome as it is specified by the coded messages in mRNA. Transfer RNA carries amino acids to the ribosome and matches them to the coded mRNA message. There is one specific tRNA for each amino acid.

9. http://www.youtube.com/watch?v=NJxobgkPEAo

10. Transcription • mRNA – stands for messenger RNA • it is the copy of the DNA message for making a protein • Occurs in the nucleus • Promoter region on DNA marks where transcription should start and terminator region marks where it should stop

11. Basic Principles of Transcription and Translation • Transcription • Is the synthesis of RNA under the direction of DNA • Produces messenger RNA (mRNA) • In transcription, segments of DNA serve as templates to produce complementary RNA molecules. • In eukaryotes, RNA is produced in the cell’s nucleus and then moves to the cytoplasm.

12. Transcription requires an enzyme known as RNA polymerase. • RNA polymerase • Binds to DNA during transcription and separates the DNA strands. • It uses one strand of DNA as a template to create a complementary strand of RNA.

13. RNA polymerase only binds to promoters, which are regions of DNA that have specific base sequences. • Before it becomes mRNA, it is called pre-mRNA. Pre-mRNA molecules have bits and pieces cut out of them before they can go into action. The portions that are cut out are calledintrons. • The remaining pieces, known as exons, are then spliced back together to form the final mRNA.

14. Genes have a complex internal organization • Introns-DNA sequences present in some genes that transcribed BUT are removed during processing and therefore are not present in mRNA. • Exons-DNA sequence that are transcribed and joined to other exons during mRNA processing and are translated into amino acid sequence of a protein

15. 19. Processing Pre-mRNA

17. Nuclear envelope DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA Ribosome TRANSLATION (b) Eukaryotic cell. The nucleus provides a separatecompartment for transcription. The original RNAtranscript, called pre-mRNA, is processed in various ways before leaving the nucleus as mRNA. Polypeptide • In eukaryotes • RNA transcripts are modified before becoming true mRNA

18. mRNA No T (thymine) so when it reads the nucleotide A on DNA it matches it with ____?

19. Protein Synthesis= transcription and translation DNA contains all the information for your traits – the genes These genes are blueprints and need to remain safe – kept inside the nucleus Copies can be made though – a messenger http://www.youtube.com/watch?v=NJxobgkPEAo

20. Section 13.2 Ribosomes and Protein Synthesis Proteins are made by joining amino acids together into long chains called polypeptides. 20 different amino acids are commonly found in polypeptides. RNA contains four different bases: Adenine, cytosine, guanine, and uracil.

21. Codons The genetic code is read three letters at a time, so that each words is three bases long and corresponds to a single amino acid. Each three letter “word” is called a codon.

22. How to Read Codons Most amino acids can be specified by more than one codon. UUA, UUG, CUU, CUC, CUA, and CUG all code for leucine. It’s time to code! Look at page 367 of your book and follow the steps in figure 13-6.

23. Start and Stop Codons The start (initiation) codon for protein synthesis is AUG, which codes for the amino acid, methionine. mRNA continues to be read, three bases at a time, until it reaches a stop codon. This ends translation and the polypeptide is complete.

24. Let’s practice coding! If given the following DNA sequence, determine the mRNA sequence transcribed for this gene. Then determine the amino acid sequence of the polypeptide using the codon chart. DNA: T A C A A G T C C A C A A T C

25. DNA: T A C G A C A A G T C C A C A A T C mRNA: A U G C U G U U C AGG UG UU A G Leucine-phenylalanine-arginine-cysteine-stop. Wait, why did we stop? STOP codons: UAA, UAG, UGA

26. Translation mRNA gives instructions on the order in which amino acids should be joined to produce a polypeptide. Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains. Translation is the process of decoding an mRNA message into a protein.

27. Transcription is carried on in the cell’s nucleus. Translation is carried out by ribosomes after the transcribed mRNA enters the cell’s cytoplasm.

28. Steps to Translation 1. Translation begins when a ribosome attaches to an mRNA molecule in the cytoplasm. 2. tRNA brings the proper amino acid into the ribosome. One at a time, the ribosome attaches these amino acids to the growing chain.

29. A Little Info about tRNA Each tRNA molecule carries just one kind of amino acid and it contains three unpaired bases. These are called the anticodon. HOLD UP Mrs. Wald…. WHAT?! A codon and an anticodon? Please explain.

30. Anticodon

31. DNA TRANSCRIPTION mRNA Ribosome TRANSLATION Polypeptide Amino acids Polypeptide tRNA with amino acid attached Ribosome Trp Phe Gly tRNA C C C G G Anticodon A A A A G G G U G U U U C Codons 5 3 mRNA • Molecules of tRNA are not all identical • 1. Each carries a specific amino acid on one end • 2. Each has an anticodon on the other end

32. If you are provided the codon: AUG The anticodon (which is located on tRNA) is: UAC Great, so what’s the amino acid? Do you use AUG or UAC? You use the codon, so AUG, which codes for the amino acid methionine.

33. Let’s continue with tRNA 3. The ribosome joins the amino acids in the binding sites and tRNA floats away from the ribosome. This creates a peptide chain! 4. The process continues until the ribosome reaches one of three of the stop condons.

34. 3 Forms of RNA All three forms of RNA come together during translation. mRNA carries the coded message. tRNA delivers the correct amino acid. Ribosomes are composed of roughly 80 proteins and 3 or 4 rRNA molecules. rRNA helps hold ribosomal proteins in place and locate the beginning of the mRNA message.

35. The Central Dogma of Biology Proteins have everything to do with traits! The central dogma of molecular biology is that information is transferred from DNA to RNA to protein.

36. mRNA CLICK ON PICTURE FOR ANIMATION ON TRANSCRIPTION Transcribes DNA message and carries it to ribosome RNA polymerse is the enzyme that produces it

37. tRNA Once mRNA is made it attaches to a ribosome tRNA = transfer RNA and they carry amino acids Amino acids are the building blocks of proteins (remember?)

39. Gene 2 DNA molecule Gene 1 Gene 3 DNA strand (template) 5 3 A C C T A A A C C G A G TRANSCRIPTION A U C G C U G G G U U U 5 mRNA 3 Codon TRANSLATION Gly Phe Protein Trp Ser Amino acid • During transcription • The gene determines the sequence of bases along the length of an mRNA molecule

40. Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA

41. From the DNA sequence below, write the complementary DNA sequence: • TGA TTT CGG TAC GAT TAA CAA CCT CGA ATT • ACT AAA GCC ATG CTA ATT GTT GGT GCT TAA • If the top DNA strand encodes the message to make a protein, then what will the transcribed M-RNA be: • ACU AAA GCC AUG CUA AUU GUU GGA GAU UAA

42. Codon = mRNAAnti-codon = tRNA

43. 3 A Amino acid attachment site C C 5 A C G C G C G U G U A A U U A U C G * G U A C A C A * A U C C * G * U G U G G * G A C C G * C A G * U G * * G A G C Hydrogen bonds (a) G Two-dimensional structure. The four base-paired regions and three loops are characteristic of all tRNAs, as is the base sequence of the amino acid attachment site at the 3 end. The anticodon triplet is unique to each tRNA type. (The asterisks mark bases that have been chemically modified, a characteristic of tRNA.) C U A G * A * A C * U A G A Anticodon • A tRNA molecule • Consists of a single RNA strand that is only about 80 nucleotides long • Is roughly L-shaped

44. Molecular Components of Translation • A cell translates an mRNA message into protein • With the help of transfer RNA (tRNA) http://highered.mcgraw-hill.com/sites/dl/free/0072437316/120060/ravenanimation.html

45. Molecular Components of Transcription • RNA synthesis • Is catalyzed by RNA polymerase, which pries the DNA strands apart and hooks together the RNA nucleotides • Follows the same base-pairing rules as DNA, except that in RNA, uracil substitutes for thymine

46. Comparing RNA & DNA X X X X X X X X

47. Comparing RNA & DNA X X X X X X X

48. Comparing RNA & DNA X X X X X X X

49. DNA RNA Concept Map RNA can be mRNA rRNA tRNA also called which functions to also called which functions to also called which functions to Brings amino acids to the ribosome Messenger RNA Carry instructions Ribosomal RNA Combine with protein Transfer RNA from to to make up Ribosomes Ribosomes