GEN 3000 Exam 2 2016 Study Guide Chapters 9 and 11 Dr Tsai Clemson University Modeled around Dr Tsai s recommended subjects to study color coded organized by chapter Exam 2 Chapters 9 and 11 Chapter 9 DNA Structure and Analysis Four qualifications of Genetic Material o Must be capable of being replicated faithfully o Must encode and store complex information o Must contain enough information to yield phenotype o Must have variation as a result of mutation Transforming principle The hypothesized factor involved in the transformation of genetic material o Griffith o Avery MacLeod McCarty Used Streptococcus pneumonia found that the virulent strain S had a smooth polysaccharide coat The antivirulent strain R lacked a coat entirely When heat killed S strain was combined with a viable R strain some R could spontaneously S Griffith concluded that some type of interaction had taken place between the viable R strain and the heat killed S strain to allow for virulent S to be produced He called this unknown material the Transforming Principle In 1944 these three scientists isolated what they believed to be the transforming principle and what they believed to be DNA They used both proteases protein destroying enzymes and RNases RNA destroying enzymes in cultures of the R and heat killed S strains of S pneumonia They found that this did not stop the transforming principle from working and virulent strains of S were still produced However when they used DNase DNA destroying enzymes the virulence of S was never achieved This led them to conclude that DNA was the transforming principle In 1952 these men used a T2 Bacteriophage also simply called a phage to build a case for nucleic acid as genetic material Remember viruses can hijack the genetic material and replication mechanisms of their host bacteria They will inject their own genetic material into the host cell Hershey and Chase took advantage of this In one group of bacteriophages they marked proteins with a radioactive sulfur compound and then the infected bacteria were allowed to replicate The progeny had no radioactively labeled proteins transferred In another group of bacteriophages they marked nucleic acids with a radioactive phosphorous The infected unmarked bacteria o Hershey and Chase were allowed to replicate and the progeny readily displayed the radioactive material suggesting that nucleic acids either RNA or DNA were the genetic material of cells NOTE They were able to separate the viruses and bacteriophages by centrifuging the mixture and putting it through a blender This separated the viruses and cells and stripped the coats leaving only the compounds they wished to observe Nucleic acids o Tobacco Mosaic Virus Displays the concept that RNA can act as genetic material Has a single piece of RNA surrounded by protein a very simple design We can show recombination of the RNA by washing away the protein and combining strains A and B getting hybrids o Purine vs pyrimidine structures will not be tested Purine Adenine and Guanine are the purine bases of DNA and they complement the pyrimidine bases These are larger than pyrimidines Pyrimidine Cytosine Thymine DNA and Uracil RNA are the pyrimidine bases of genetic material Matches DNA A T G C RNA A T G U Nucleotide components o Sugar Deoxyribose in DNA and Ribose in RNA These are attached to a nitrogen containing base for different variations o Base Nitrogen containing bases consist of purines and pyrimidines See above NOTE The sugar attached to its respective base is called a NUCLEOSIDE whereas a NUCLEOTIDE is a nucleoside attached to a phosphate group o Phosphate Backbone The backbone of DNA is made up of phosphate groups which are attached to the nucleosides o Types Deoxyadenosine 5 monophosphate Deoxyribose sugar adenine nitrogen Deoxyguanosine 5 monophosphate Deoxyribose sugar guanine nitrogen base attached to a phosphate dAMP base attached to a phosphate dGMP base attached to a phosphate dCMP base attached to a phosphate dTMP Deoxycitidine 5 monophosphate Deoxyribose sugar cytosine nitrogen Deoxythymidine 5 monophosphate Deoxyribose sugar thymine nitrogen Chargaff s rule o Chargaff and his colleagues were able to separate the residues of the bases of nucleic acids and found several things The amount of Guanine residue was equal to that of the Cytosine residue suggesting that this pyrimidine and purine match up in DNA The amount of Thymine residue was equal to that of Adenine residue suggesting that this pyrimidine and purine match up in DNA Due to proportionality the amount of A C T G Watson Crick Wilkins Franklin o Wilkins and Franklin Used x ray crystallography to identify the location of molecules contained in DNA This truly was the key to unlocking the secrets of DNA structure o Watson and Crick 1953 Watson and Crick used chemistry and X ray diffraction to solve DNA structure Franklin s data was key We have also been stimulated by a knowledge of the general nature of the unpublished experimental results and ideas of Dr M H F Wilkins Dr R E Franklin Proposed a double helical form of DNA made of matched pyrimidine and purine bases If it were made of just matched purines the structure would be too thick If it were made of just matched pyrimidines the structure would be too thin The complementary bases instead matched the models put together by W and C DNA characteristics o Bonds o Directionality Hydrogen bonds Between the nitrogen containing bases pyrimidines and purines hydrogen bonds are formed There are three H bonds between G and C and two H bonds between A and T The fewer H bonds the weaker the bond is and the more easily it is broken These H bonds are hydrophobic These weaker bonds allow for the opening of DNA for replication translation transcription Phosphodiester Bonds The sugarphosphate backbone of DNA is connected by phosphodiester bonds which are incredibly strong and hydrophilic This keeps the DNA shape and is very hard to break The helical formation of DNA is made of two complementary strands These strands run antiparallel to each other The 5 end of one ending with a phosphate matches to the complementary 3 end ending with a sugar of the other strand The nitrogen containing bases are in between these strands and are connected by hydrogen bonds NOTE DNA can only replicate 5 to 3 This is very important Will start at the 3 end of the strand so that the 5 end of the new strand can begin This alternating complementary strand winds in a right handed or clockwise spiral