Chapter 10 Nucleic Acids & Protein Synthesis

1. Chapter 10Nucleic Acids& Protein Synthesis

2. After completing the chapter on Genetics, we discussed the passing on of genes, but how are genes produced?

3. Brief history of DNA Frederick Griffith – 1928 • Experimented with pneumonia bacteria. Grew 2 strains of bacteria • 1 formed smooth colonies and causing pneumonia • The other forms rough colonies and is harmless. Heat kills disease causing strain - mice don’t get pneumonia. Injects rough, harmless strain into mice, mice are fine. Adds heat killed harmful strain to the harmless strain injected into mice. The mice die. He cultures the bacteria. Finds that the harmless rough bacteria had been “transformed” or changed into the lethal strain.

4. Griffith’s Transformation Experiment

6. Conclusion • Theharmless bacteriaweretransformedby some factor from the harmful bacteria • Did not know what that factor was though

7. Oswald Avery and company 1944 • Repeated Griffith’s work but used enzymes (lipases, proteases and carboases) to destroy proteins, lipids and carbs in the heat killed bacteria. • Pneumonia and transformation still occurred. • Then used an enzyme to kill RNA. Still transformed. • Finally, used an enzyme to break apart DNA. • This stopped transformation

9. Conclusion • DNA is the nucleic acid that stores and transmits genetic information.

10. Hershey and Chase – 1952 • Used T4 bacteriophage virus that infectsE. colibacteria to study viral inheritance • A virus is a non-living pathogenic particle that can’t replicate on its own Capsid (protein)

11. The Lytic Cycle of Virus infection Attaches onto host cell Injects DNA into host cell Replication of Viral parts Reassembly of virons Lysis – bursting out

12. What part of a virus actually infects & causes the host cell to become a viral factory? Used radioactive isotopes of P31 and S32. P32 and S35 Proteins may contain sulfur but do not have Phosphorus DNA is made up of Phosphate groups but doesn’t contain Sulfur

13. Used P32 Used S35 Found that the S35 stayed outside the cell & P32 ended up in new virons Animation

14. Conclusion The genetic material of the bacteriophage is located in the DNA, not the protein coat

15. Erwin Chargaff – 1940’s Noticed a pattern in the amounts of the four bases: Adenine, Guanine, Cytosine, and Thymine • Found the number of Guanine & Cytosine nitrogen bases is always equal in DNA • & the number of Thymine and Adenine is always equal. • Didn’t know why though!

16. History of DNA: • Rosalind Franklin took X-Ray diffraction photo (Photo 51) of DNA. • Determined that DNA was a double helix with the bases in the center.

17. Watson and Crick (1953) • Using Franklin’s Photo 51, came up with the double helix form of DNA. Won Nobel Price w/ Maurice Wilkins (1962). Original DNA model.

20. Crick & Watson's DNA Model

21. Structure of DNADeoxyribonucleic acid Polymer of the monomer – Nucleotides 5 carbon sugar –Deoxyribose A phosphate group A nitrogen base P S N-base Nucleotide Sugar & phosphate alternate to make up the sides of the strand Found only in nucleus Single nucleotide

22. 4 nitrogen bases • Guanine - Purine • Cytosine - Pyrimidine • Adenine - Purine • Thymine - Pyrimidine Follow base pairing rule Adenine with Thymine Guanine with Cytosine Bases are held together by weak hydrogen bonds N-bases connect to sugars by a covalent bond

23. Nitrogen base Phosphate group Covalent bond 5 Carbon sugar Weak H bond

24. In Cell Reproduction, we keep mentioning DNA replication. How does DNA do this? • Occurs during Interphase – Makes 2 exact copies of the original. If not, a mutation occurs. • The double helix unwinds and flattens out (like a zipper) • An enzyme DNA helicase (like the zipper slide) unzips the strand at the weak hydrogen bonds. This exposes the Nitrogen bases (each tooth of the zipper) • Another enzyme, DNA polymerase will be responsible for rezipping the strands. It will take free nucleotides in the nucleus and bond them to the exposed bases, following the base pair ruling – G – C and A – T. • The base pairing continues until the entire strand has their complement. • Now there are two identical strands of DNA Animation

25. DNA helicase unzips Original (old) strands of DNA are on the outside of the new strands. Replicates from the center with aid of DNA polymerase Semi-conservative model Side 1 25971 GLENN!!!

26. c c Here is a song

27. How good at replicating is DNA? • Accurate to about 1 error for every 10,000 base pairs. With DNA “ proof-reading” and repair, brings # of errors to only 1/1 billion • Rate of 40 bases per second!!!! • Gene Mutation – error resulting from misread of DNA or problem in the translation process later on. (We’ll come back to this later)

28. RNA Ribonucleic acidThe other Nucleic Acid • Acts as a messenger between DNA and the ribosomes and carries out protein synthesis • DNA is too large to get out of the nucleus. Uses RNA to bring its message to the rest of the cell for protein synthesis

29. How DNA & RNA Differ RNA is single stranded helix Has Ribose sugar instead of Deoxyribose Contains Uracil in place of Thymine so Adenine bonds with Uracil Can be found in the nucleus, cytoplasm or at the ribosomes

30. Three different kinds of RNA • Messenger RNA (mRNA) Formed in the nucleus & goes to the ribosomes. Carries genetic code from DNA, through the cytoplasm to the ribosomes • Transfer RNA (tRNA) – t-shaped. Carries amino acids to the mRNA in the ribosomes. • Ribosomal RNA (rRNA) Most abundant. RNA in globular form. Makes up the ribosomes

31. Messenger RNA (mRNA) • Since DNA is too large to leave the nucleus, it must use mRNA to get it’s message out • mRNA nucleotides are free in the nucleoplasm • RNA polymerase allows for mRNA synthesis to compliment DNA • If DNA is: CTA CGG AGA, • mRNA is: GAU GCC UCU (Remember, U substitutes for T in RNA) • This is called Transcription.

32. Transfer RNA (tRNA) • Are free in cytoplasm • Go to the ribosomes to get DNA’s message from the mRNA • Transfer amino acids from the cytoplasm to the ribosomes

33. Ribosomal RNA (rRNA) • Found only making up the ribosomes. • Responsible for overseeing that the process of Protein synthesis occurs properly.

34. Now for DNA’s real job.DNA rap • Protein synthesis • Process by which DNA codes for the production of proteins (polypeptide chains) & protein assembly Polypeptide chains are polymers of the 20 different amino acids. Genetic code – Coded for on the DNA that translates into the production of a polypeptide chain made up of amino acids

35. Overall look Amino Acid Polypeptide forming Translation Transcription

36. 1. Process begins in the nucleus w/ the Transcription of DNA by mRNA • DNA flattens and is unzipped exposing its bases (template) • RNA polymerase binds free RNA nucleotides to exposed DNA bases starting at a promoter – TAC (like a capital letter at start of a sentence). • Base rule pattern is the same as in replication w/ the exception of Thymine. THERE IS NO THYMINE IN RNA. Instead, Adenine bonds with Uracil and Thymine from DNA would bond with Adenine. • Transcription continues until a termination signal is given (like a period) to stop the transcription process • If DNA reads: ATC GTC GAT TGG C AA • mRNA: UAG CAG CUA ACC GUU • mRNA leaves the nucleus through a pore to go out into the cytosol to a ribosome

37. At the ribosome, the process of Translation occurs. • mRNA will temporarily bind with the ribosome • Starting with the start codon(AUG), in groups of 3, mRNA will determine which Amino acid tRNA must bring to the ribosome. • Animation – Virtual Cell

38. Polypeptide forming Transcription Translation Central Dogma Song Sing along - YouTube

39. Codons are groups of 3 adjacent bases on mRNA (AAA, CCC GGG) • Each codon will specify a specific Amino Acid. This is called Translation. 64 different codons • Free floating amino acids in the cytosol are transported to mRNA by tRNA. • tRNA attaches to mRNA by the anticodon • If DNA reads:A T G G T C G A T T G G CAA • mRNA: U A C C A G C U A A CC GUU • tRNA: A U G G U C G A U U GG CAA • Translation: • Amino Acid: Tyrosine - Glutamine – Leucine -Threonine - Valine

40. Stop Codons The Genetic Code Start codon

41. DNAmRNAProtein TranscriptionTranslation Protein Synthesis

42. Once tRNA brings the correct amino acid to mRNA at the ribosome, it releases to go & get more amino acids. • Adjacent amino acids bond together at a peptide bond to form a polypeptide. • Chain could be up to 10,000 amino acids long • tRNA with the anticodon (complimentary to mRNA) links to mRNA. It carries a specific Amino Acid (specified by mRNA).

43. When adjacent Amino Acids link together, they form a peptide bond. • The first tRNA releases, then the next codon goes into place and another Amino Acid is brought in by a tRNA. This continues until the entire message is translated. • The chain of Amino Acids is formed called a Polypeptide (protein). The translation ends when a STOPcodon is reached (UAA, UAG, UGA).

44. DNA codes for mRNA, • mRNA carries the information needed for the synthesis of coded proteins in the ribosomes. • tRNA is the go-for that brings the amino acids to the ribosomes to make the protein). Side 1 22695

47. Protein Synthesis • Production of Proteins coded for by DNA • AnimationProtein Synthesis - Learning • You tube animation– really good! • McGraw animation • http://www.youtube.com/watch?v=41_Ne5mS2ls – HHMI one • Replication & Protein synthesis – song with only typed words but good • Central Dogma Song

48. Does this process ever make a mistake? • Have you ever had to copy a large amount of information? • What is the likelihood of you making a mistake or more? • What could cause these changes?

49. Mutation Changes in genetic material Gene Mutations: alters one or more genes Chromosomal Mutations: alter the entire chromosome or a portion of it.

50. Gene Mutations Point Mutations – affect only one amino acid Frameshift mutations – May affect an entire amino acid sequence.