BIOL 302 1st Edition Lecture 4 Outline of Last Lecture I. General Protein functionA. Amino acidsB. Hydrophobic interactionsII. Protein StructureA. Denaturation, prion diseasesB. Folding patternsC. Levels of organizationIII. Feedback InhibitionA. Allosteric proteinsB. PhosphorylationC. Nucleotide hydrolysisD. Affinity chromatographyOutline of Current Lecture I. Discovery that DNA was genetic materiala. James Watson and Francis Crickb. Rosalind Franklinc. Fred GriffithII. DNA structurea. Chromosomes, chromatidb. Nucleotide building blocksc. Hydrogen bondsd. Double helixe. Hershey & Chasef. Genes, genomeIII. DNA packinga. Chromatinb. Nucleosomesc. Genesd. Histone molecules, histone modificationCurrent LectureCh. 5 DNA and ChromosomeThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Life depends on the ability of a cell to store, retrieve, and translate the genetic instructions, which are required to make and maintain a living organism. - Hereditary info is passed on from a cell to its daughter cells, from generation to generation.- These instructions are stored within every living cell in its genes that determine the characteristics of a species as a whole and of individuals within it. - 1940s: DNA recognized as possible carrier of genetic info.- 1953: James Watson and Francis Crick determined the DNA structure and revealed how DNA might be copied and encodes instructions for making proteins.o They submit a one page paper to the journal Nature stating, “It has not escaped out notice that the specific pairing that we have postulated immediately suggestsa possible copying mechanism for the genetic material.”- Rosalind Franklin obtained excellent X-ray diffraction patterns of crystalline B-form DNA and discovered important basic facts about its structure. She died in April of 1958, the Nobel Prize is not awarded after death. o After her death, Watson and Crick made clear in public lectures that they could not have discovered the structure of DNA without her work. o In 2004, Finch University of Health Sciences/Chicago Medical School changed its name to “Rosalind Franklin University of Medicine and Science” to honor her contribution to science. Discovery that DNA was the genetic Material- 1920s: (before discovery of antibiotics) Fred Griffith performed an experiment using two strains of pneumococcal bacterium (causes pneumonia)- the pathogenic strain (S strain) and the non-lethal strain (R-strain). He injected the strains into mice and analyzed their effects. He discovered that if he heat-killed the pathogenic strain and injected it into the mouse, the bacterium were no longer able to cause infection. - He injected the heat killed pathogenic strain and the harmless strain together. This combo proved lethal for the mice, causing them to develop pneumonia and have lethal amounts of bacteria in their blood. The heat-killed pathogenic strain had converted the harmless strain into the lethal for. He set off to discover how this “transformation” was occurring. - Years later, after purifying the material from the bacterium that caused the transformation of the harmless strain to the lethal strain, the purified material was analyzed and it was discovered that the main component of the purified substance was DNA. This allowed scientists to conclude that DNA was the stuff of which genes are made.- Up until this discovery, researches assumed that proteins housed the genetic info because of their complexity. A simple molecule like DNA couldn’t possibly be responsiblefor housing all of the genetic info needed by living organisms. Experiments were continued and it was discovered that enzymes that destroy RNA and proteins had no effect on the purified substances ability to transform bacteria, while enzymes that destroy DNA inactivated the substances ability to transform the bacteria. Before biologists understood the structure of DNA, they already recognized that inherited traits and the genes associated with them were associated with chromosomes. Chromosomes were already known to contain DNA and protein complexes, but structural and functional organization was not yet known. - The complex of DNA and protein packed into chromosomes is called CHROMATIN (remember this term)- Chromosomes were discovered in the 19th century and described as “threadlike structures in the eukaryotic cell nucleus that become visible as the cell divides”DNA is made of four nucleotide building blocks - Nucleotides are the building blocks/monomers of nucleic acids- Each nucleotide is composed of a sugar phosphate covalently linked to a nitrogenous base. The covalent linkage between the sugar phosphate backbone forms a phosphodiester bond. - Nucleotides are covalently linked together into polynucleotide chains, with a sugar phosphate backbone from which the bases (A, C, G and T) extend.- A- adenine, C-cytosine, G-guanine, T-thymine- Nucleotide= sugar phosphate covalently linked to a base- Nucleoside=sugar covalently linked to base, NO phosphate group- Covalent bonds are formed between 5’ and 3’ Carbons on sugars, and link nucleotides together forming the polynucleotide chain. The 5’ and 3’ positions help to provide directionality and polarity to the polynucleotide chain. - DNA is made of four building blocks: A DNA molecule is composed of two polynucleotidechains (DNA strands) held together by hydrogen bonds between the paired bases. The four bases for complementary pairs held together through non covalent hydrogen bonds. Purines (double ring nitrogenous base, A and G) pair with pyrimidines (single ringnitrogenous bases, C and T). A always pairs with T, C always pairs with G. Hydrogen bonds between complementary base pairs hold together the two strands of DNA double helix:- 2 H bonds form b/w A and T, and 3 H bonds form b/w G and C- In each case, a two ring base (purine) is paired with a single ring base (pyrimidine)- Each purine-pyrimidine pair is called a base pair- The 3’ end carries a free phosphate group attached to the 5’position on the sugar ring; the 5’ end carries a free phosphate group attached to the 5’ position on sugar ring. This allows the DNA molecule to have a polarity, where the DNA is always “read” going in the 5’ to 3’ directionThe DNA double helix conformation- The two strands of DNA wind around each other to form