GN 311 EXAM 2 QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026

GN 311 EXAM 2 QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026 Major Question: Griffith - Answers Why do nonvirulent strains of S. pneumonia become virulent when exposed to dead virulent strains? Major Question: Avery, Macleod and McCarty - Answers What is the cause of transformation from Griffith's experiments? Major Question: Hershey and Chase - Answers What are the infectious parts of bacteriophages? Major Question: Chargaff - Answers What is the base composition of DNA and is there a pattern? Major Question: Wilkins and Franklin - Answers What is the crystalline structure of DNA? Major Question: Watson and Crick - Answers What is the structure of DNA? Simple Idea: Griffith - Answers Can an extract from dead bacterial cells genetically transform living cells? Simple Idea: Avery, Macleod and McCarty - Answers Eliminate each component of bacteria one at a time. If the nonvirulent strain is transformed, the components removed are not needed for transformation Simple Idea: Hershey and Chase - Answers Radiolabel phages protein coat (35S) or DNA (32P). Observe what gets passed on. Simple Idea: Chargaff - Answers Did a quantitative analysis of DNA base pairs Simple Idea: Wilkins and Franklin - Answers X-ray crystallography study of DNA Simple Idea: Watson and Crick - Answers Used Chargaff's and Franklin's data + others to determine DNA structure Key Observations: Meischer - Answers First to isolate DNA Key Observations: Yanofsky - Answers Changes in DNA and protein are colinear Key Observations: Griffith - Answers S strain kills mice, Heat-killed S strain does not kill mice, R strain does not kill mice, Heated S + R strain does kill mice Key Observations: Avery, Macleod and McCarty - Answers Only treatment of the S cell extract with DNase kept the extract from transforming the R cells. Key Observations: Hershey and Chase - Answers The bacteria had a lot of 32P and very little 35S after phage infection Key Observations: Chargaff - Answers Base composition from different species in table. Key Observations: Wilkins and Franklin - Answers X-ray scattered picture of crystallized DNA looks like a helix 2 nm in diameter with 2 regularities: 3.4 nm and 0.34 nm Key Observations: Watson and Crick - Answers KNOWN: Chargaff Ratios, DNA is helical (Franklin); Hydrogen bonds set the structure of the DNA Conclusions: Griffith - Answers The unknown process that changes the avirulent strain to a virulent strain is called Transformation Conclusions: Avery, Macleod and McCarty - Answers DNA is required for transformation. Conclusions: Hershey and Chase - Answers DNA is the infectious part of bacteriophages Conclusions: Chargaff - Answers G=C (amount) A=T (amount) Conclusions: Wilkins and Franklin - Answers Structure of DNA is helical w/ more than one helix with repeating patterns Conclusions: Watson and Crick - Answers Antiparallel strands. Pyrimidines pair with purines. Sugars and phosphates on the outside of the helix. Alternating major and minor grooves. 2 nm wide. 3.4 nm per turn of helix. 0.34 nm between adjacent bases. ETC. Imagine you are a student in Alfred Hershey and Martha Chase's lab in the late 1940s. You are given five test tubes containing E. coli bacteria that were infected with T2 bacteriophage that have been labeled with either 32P or 35S. Unfortunately, you forgot to mark the tubes and are now uncertain which were labeled with 32P and which with 35S. You place the contents of the each tube in a blender and turn it on for a few seconds to shear off the protein coats. You then centrifuge the contents to separate the protein coats and the cells. You check for the presence of radioactivity and obtain the following results. Which tubes contained E. coli infected with 32P labeled phage? Tube number Presence of radioactivity 1 cells 2 protein coats 3 protein coats 4 cells 5 cells - Answers Tubes 1, 4, and 5. The DNA of the bacteriophage contains phosphorous and the protein contains sulfur. When the bacteriophages infect the cell, they inject their DNA into the cell, but the protein coats stay on the surface of the cell. The protein coats are sheared off in the blender, while the cells with the DNA pellet at the bottom of the tube. Thus, cells infected with 35S -labeled bacteriophage will have radioactivity associated with the protein coats, whereas those cells infected with 32Plabeled bacteriophage will have radioactivity associated with the cells. What results would you expect if the bacteriophage that Hershey and Chase used in their experiment had contained RNA instead of DNA? - Answers The results would be the same. RNA, like DNA, contains phosphorus but not sulfur, so the 32P would have been incorporated into the RNA and entered the cell hosts during the course of the infection. Ultimately the 32P would be incorporated into the RNA of progeny phage during the course of phage reproduction. Protein contains sulfur but not phosphorus, so 35S would have been assimilated into the phage protein coat; it would have remained with the viral coats that do not enter the cells and not transferred to progeny phage. The 35Scontaining protein coats would still be recovered in the fluid recovered following centrifugation In a typical eukaryotic cell, would you expect to find more molecules of the H1 histone or more molecules of the H2A histone? - Answers Because each nucleosome contains two molecules of histone H2A and only one molecule of histone H1 is associated with each nucleosome, eukaryotic cells will have more H2A than H1. Would you expect to find more molecules of H2A or more molecules of H3? - Answers Because each nucleosome contains two molecules of H2A and two molecules of H3, eukaryotic cells should have equal amounts of these two histones. Replication: Where does this process occur in a eukaryotic cell? - Answers Nucleus Replication: What is the enzyme that carries out this process? - Answers DNA Polymerase Replication: What is the template that is read during this process? - Answers DNA Replication: In what direction is the template read? - Answers 3' to 5' Replication: What is the start signal/sequence for this process? - Answers Origin Replication: What is the polymer that is formed? - Answers DNA Replication: What monomer is used to form this polymer? - Answers deoxyribonucleotides Replication: What type of bond is formed between monomers? - Answers Phosphodiester Replication: In what direction is the new polymer formed? - Answers 5' to 3'