1. FROM DNA TO PROTEINS Chapter 8

2. KEY CONCEPT 8.1 DNA was identified as the genetic material through a series of experiments.

3. GRIFFITH FINDS A ‘TRANSFORMING PRINCIPLE’ (GENETIC MATERIAL). 1928 Griffith experimented with the bacteria that cause pneumonia and discovered transformation – when genetic material is passed from one bacteria to another He used two forms: the S form (deadly) and the R form (not deadly). A transforming material passed from dead S bacteria to live R bacteria, making them deadly.

6. AVERY IDENTIFIED DNA AS THE GENETIC MATERIAL. 1944 DNAase, an enzyme that breaks down DNA, prevents transformation. Therefore, DNA must be the genetic material –Tests showed DNA was present. –Enzyme tests showed only DNA-degrading enzymes stopped transformation.

7. HERSHEY AND CHASE CONFIRM THAT DNA IS THE GENETIC MATERIAL. 1952 Hershey and Chase studied viruses that infect bacteria, or bacteriophages. *Tagged DNA was found inside the bacteria; tagged proteins were not. Therefore DNA is genetic material. – They tagged viral DNA with radioactive phosphorus. – They tagged viral proteins with radioactive sulfur.

9. ROSALIND FRANKLIN AND MAURICE WILKINS Franklin’s x-ray images suggested that DNA was a double helix of even width and that molecules are spaced at regular intervals X- shape in crystallography image X-Ray Diffraction Image of DNA

10. EDWARD CHARGAFF (1950) Number of adenine molecules = the number of thymine molecules (A=T) Number of guanine molecules = number of cytosine molecules (C=G)

11. Chargaff's Rules Erwin Chargaff showed that the percentages of guanine and cytosine in DNA are almost equal. The same is true for adenine and thymine.

12. WATSON AND CRICK DETERMINED THE THREE- DIMENSIONAL STRUCTURE OF DNA BY BUILDING MODELS. 1953 Building blocks of DNA are nucleotides DNA is a double helix (twisted ladder) Composed of a sugar- phosphate backbone on the outside with bases on the inside.

15. KEY CONCEPT 8.2 DNA structure is the same in all organisms.

16. DNA Recall that: DNA controls cell functions and inheritance of traits Forms chromosomes in the nucleus DNA is wrapped around proteins, called histones

18. DNA IS COMPOSED OF FOUR TYPES OF NUCLEOTIDES. DNA is made up of a long chain of nucleotides. Each nucleotide has three parts.  a phosphate group  a deoxyribose sugar  a nitrogen-containing base phosphate group deoxyribose (sugar) nitrogen-containing base

19. The nitrogen containing bases are the only difference in the four nucleotides.

20. PURINES AND PYRIMIDINES: Purines- Adenine and Guanine are double rings, formed from a 5 carbon ring fused to a 6 carbon ring (both contain nitrogen) Pyrimidines - Thymine and Cytosine made of a single ring of carbon and nitrogen

22. T A C G NUCLEOTIDES ALWAYS PAIR IN THE SAME WAY. The base-pairing rules show how nucleotides always pair up in DNA. Because a pyrimidine (single ring) pairs with a purine (double ring), the helix has a uniform width. – A pairs with T – C pairs with G

23. The backbone is connected by covalent bonds. hydrogen bond covalent bond The bases are connected by weak hydrogen bonds.

24. Aand T always pair together with 2 hydrogen bonds. G and C pair with 3 hydrogen bonds. The two sugar-phosphate backbones run in opposite directions (antiparallel)

26. KEY CONCEPT 8.3 DNA replication copies the genetic information of a cell.

27. REPLICATION COPIES THE GENETIC INFORMATION. A single strand of DNA serves as a template for a new strand. The rules of base pairing direct replication. DNA is replicated during the S (synthesis) stage of the cell cycle. Each body cell gets a complete set of identical DNA.

28. PROTEINS CARRY OUT THE PROCESS OF REPLICATION. DNA serves only as a template. Enzymes and other proteins do the actual work of replication. Enzymes unzip the double helix. Free-floating nucleotides form hydrogen bonds with the template strand.

29. ANTIPARALLEL STRANDS The end with the phosphate group attached to the ending sugar is called the 5’ end The 3’ end has an OH group attached to the #3 carbon on the sugar DNA polymerase only attaches to an OH group 3’, thus replication proceeds from 3’ toward 5’ end along the original strand; the new strand forms 5’ to 3’

31. STEPS OF REPLICATION: 1. DNA unzips with the help of helicase. 2. Helicases break hydrogen bonds between base pairs forming a replication fork. nucleotide The DNA molecule unzips in both directions.

32. STEPS OF REPLICATION (CONTINUED): 3. DNA polymerase forms a new complementary strand for each old strand by adding nucleotides. Covalent bonds form between the nucleotides. ex: Old Strand: A G G G G C G A C New Strand: DNA polymerase new strand nucleotide

33. original strand new strand Two molecules of DNA 4. DNA polymerase also proofreads the strands to ensure accuracy. 5. Two new molecules of DNA are formed, each with an original strand and a newly formed strand. Steps of Replication (Continued):

34. There are many origins of replication in eukaryotic chromosomes. DNA replication starts at many points in eukaryotic chromosomes. REPLICATION IS FAST AND ACCURATE. DNA polymerases can find and correct errors.

35. KEY CONCEPT 8.4 Transcription converts a gene into a single-stranded RNA molecule.

36. CENTRAL DOGMA: DNA mRNA PROTEIN The central dogma states that information flows in one direction from DNA to RNA to proteins.

38. RNA - RIBONUCLEIC ACID 1. RIBOSE is the sugar 2. Uracil (another pyrimidine) replaces thymine 3. Single strand 4. 3 types of RNA

39. Types of RNAFunction Messenger RNA (mRNA) carries the message that will be translated to form a protein. Transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome. Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made.

40. DIFFERENCES BETWEEN DNA AND RNA: DNARNA 1. thymine1. Uracil 2. double strand 2. single strand 3. deoxyribose3. ribose 4. found in the nucleus 4. in entire cell 5. larger5. smaller 6. unzips and replicates 6. forms off of DNA

41. PROTEIN SYNTHESIS OVERVIEW: ONLINE ACTIVITY What is a protein? http://learn.genetics.utah.edu/units/basics/transcribe/

42. 1. RNA polymerase and other proteins form a transcription complex, which recognizes the start of a gene and unwinds a segment of it. 2. Transcription: RNA polymerase makes complementary copy of a section of DNA, forming single-stranded mRNA 3. mRNA is edited and goes to ribosome ex: DNA strand: A A T T G G C C C mRNA copy: U U A A C C G G G Step 1: Transcription

43. start site nucleotides transcription complex Transcription:

44. DNA RNA polymerase moves along the DNA

45. RNA

46. THE TRANSCRIPTION PROCESS IS SIMILAR TO REPLICATION: Similarity: Transcription and replication both involve complex enzymes and complementary base pairing. Differences:  Replication copies all the DNA; transcription copies a gene.  Replication makes one copy; transcription can make many copies. growing RNA strands DNA one gen e