Chapter 10: DNA Structure & Analysis-Questions & Answers 100% Verified
Chapter 10: DNA Structure & Analysis-Questions & Answers 100% Verified What was the initial lead to DNA acceptance as genetic material? - ANSWER-the chemical nature on the "transforming principle" in bacteria publication by Avery, Macleod & McCarty; beginning of the era of molecular genetics What did Frederick Griffith work with (1920s)? - ANSWER-He worked with different strains of bacteria called Diplococcus Pneumoniae Explain the difference between the IIR & IIIS colonies. - ANSWER-IIR: rough colony with an absent capsule that was noninfectious (avirulent) IIIS: smooth colony with a present capsule that was infectious (virulent) What does a no capsule mean? capsule? - ANSWER-With no capsule, bacteria are killed by phagocytes of host immune system. But with it, bacteria are not easily engulfed by phagocytes. The capsule has a polysaccharide coating making it hard for immune systems to identify the bacteria & destroy it. Griffith: Injects Living S cells - ANSWER-produces pneumonia, mouse dies Griffith: Injects Living R cells (rough) - ANSWER-mouse is healthy and lives Griffith: Injects heat-killed S cells - ANSWER-mouse is healthy and lives Griffith: mixture of heat-killed S cells & living R cells - ANSWER-mouse dies; analysis of blood revealed a large # of LIVING type IIIS (virulent) bacteria Avery, Macleod & McCarty Experiment - ANSWER-Reported they had obtained the transforming principle in a purified state & that surely it was DNA -Used large quantities of liquid cultures of IIIS virulent cells (they centrifuged, extracted, filtrated). They discovered the active factor to be DNA as they induced type IIR cells. How did the Avery, McCarty, MacLeod experiment discover DNA? - ANSWER-Mass showed similarity for N:P ratio with sodium deoxynucleate - chemical name for DNA Hershey & Chase Experiment - ANSWER-Study of bacterium Escherichia Coli and one of its infecting viruses, bacteriophage T2 (consists of a protein coat surrounding a core of DNA; exterior is composed of a hexagonal head + a tail). What was known before they Hershey & Chase Experiment? - ANSWER-T2 phages consists 50-50% protein to DNA -Infection is initiated by a adsorption of the phage by its tail fibers tot the bacteria cell -production of new viruses occurs within bacterial cell
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