Chapter 10 DNA, RNA and Protein Synthesis

1. Chapter 10DNA, RNAand Protein Synthesis

2. Chapter 9 and 12 discuss inheritance patterns that describe how genes are passed along from parent to offspring. But what are genes composed of?

3. 10.1 Discovery of DNA Frederick Griffith– 1928 • Experimented with pneumonia bacteriacalled Streptococcus pneumoniae. There were two strains of the bacteria: • 1 formed smooth colonies and caused pneumonia (pathogenic) • The other formed rough colonies and was harmless.

4. Griffith’s Transformation Experiment

6. Grifffith’s Conclusion • The harmless bacteria were transformed by some factor from the harmful bacteria = this is called transformation - the transferring of DNA from one cell to another • Did not know what that factor was though

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

9. Avery’s Conclusion • DNA is the material that stores and transmits genetic information

10. Hershey and Chase – 1952 • Used T4 bacteriophage virus that infects E. coli bacteria • A virus is a non-living pathogenic particle that can’t replicate on its own Capsid (protein)

11. What part of a virus actually infects & causes the host cell to become a viral factory – the outside capsid or the inner DNA? Used radioactive isotopes of phosphorus and sulfur: P32 and S35 Proteins do not have phosphorus DNA does not have sulfur

12. Used P32 Used S35 • Found that the S35 stayed outside the cell & P32 ended up in new virions • Animation

13. Hershey-Chase Conclusion The genetic material of the bacteriophage is located in the DNA, not the protein coat

14. 10. 2 DNA Structure Watson and Crick (1953) Using Franklin’s photo, came up with the double helix form of DNA. Won Nobel Price w/ Maurice Wilkins (1962). Original DNA model.

15. DNA Structure • Rosalind Franklin took X-Ray diffraction photo of DNA.

16. 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!

17. 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

18. 4 nitrogenous bases • Guanine - Purine • Cytosine - Pyrimidine • Adenine - Purine • Thymine - Pyrimidine Follow base pairing rules: Adenine with Thymine Guanine with Cytosine Bases are held together by weak hydrogen bonds N-bases connect to sugars by a covalent bond

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

20. 10.3 DNA Replication: How does DNA Copy Itself? • 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 nitrogenous 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 rules: 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

21. Original (old) strand of DNA is called a template. Replicates from the center with aid of DNA polymerase Semi-conservative model because half of the new strand is the original parent strand

22. 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 • Gene Mutation – error resulting from misread of DNA or problem in the translation process later on. (We’ll come back to this later)

23. 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

24. 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

25. 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

26. 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.

27. 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

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

29. Now for DNA’s real job. • 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

30. Overall look Amino Acid Polypeptide forming Translation Transcription

31. 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

32. 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

33. Polypeptide forming Transcription Translation

34. 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

35. Stop Codons The Genetic Code Start codon

36. DNAmRNAProtein TranscriptionTranslation Protein Synthesis

37. 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).

38. 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).

39. 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

40. Protein Synthesis • Production of Proteins coded for by DNA • AnimationProtein Synthesis - Learning Activity - Flash Player Installation • Another animation • Transcription/Translation game

41. 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?

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

43. Gene Mutations Point Mutations – either a substitution or addition/deletion; if a substitution, only one amino acid will change Frameshift mutations – result from point mutations with additions/deletions and can alter the entire polypeptide chain

44. In the case of a substitution… • THE FAT CAT ATE THE RAT • Take out “C” in Cat & substitute a “B” • THE FAT BAT ATE THE RAT • Does not really change the meaning to the sentence or the protein formed

45. 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 AC C GUU • Amino Acid: Tyrosine - Glutamine – Leucine -Threonine – Valine • But if mRNA: U A C C A G C A A AC C GUU • The AA: Tyrosine – Glutamine – Glutamine – Threonine – Valine

46. Frameshift mutation • involves a change in the entire protein formed or a large portion of it. • caused by insertions (additions) or deletions of nitrogen bases = point mutations

47. THE FAT CAT ATE THE RAT • Take out “E” in THE & group into 3’s • THF ATC ATA TET HER AT_ This makes no sense at all!!

48. 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 AC C GUU • AA: Tyrosine - Glutamine – Leucine -Threonine – Valine • BUT if mRNA: U A C C A G U A A C C G U U _ • THEN Amino Acid: Tyrosine - Glutamine – STOP!!!! • The entire sentence makes no sense. The protein formed would be totally different!

49. So which form of a mutation would be more severe? • Frameshift mutation … since an entirely new protein would be formed

50. CHROMOSOMAL MUTATIONS • involve changes in number and structure of the chromosomes. • could change location of genes on the chromosomes or the number of copies of some of the genes.