Chapter 11 Study Guide

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University of Toronto Scarborough
Biological Sciences
Mark Fitzpatrick

Chapter 11: DNA and Its Role in Heredity 11.1 What is the evidence that the Gene is DNA? N By the 1920s, it was known that chromosomes consisted of DNA and proteins N A new dye provided circumstantial evidence that DNA was the genetic material: o It was in the right place o It varied among species o It was present in the right amount N The convincing demonstration that DNA is the genetic material came from two sets of experiments The Transforming Principle N Frederick Griffith was working with two strains of Streptococcuspneumonia and was trying to develop a vaccine for it N He was working with two strains of this bacteria: The S-strain (had a protective capsule) which was virulent, and the R-Z]L~o lZ} ] ZoLL[]oL N He found that after destroying the S-strain with heat, and then introducing R-strain to the pool, the R-strain turned virulent N Proved that there is a substance that causes a heritable change in R-strain What was the substance? N Oswald Avery N His experiment consisted of treating different samples of heat-killed S-strain virus with enzymes that destroy either RNA, Proteins, or DNA N And only when the DNA was destroyed was the transforming principle lost N Had little impact early on since bacterial genetics was a very new field, and people assumed DNA lacked the complexity of proteins Hershey-Chase Experiment N Determined whether DNA or protein is the genetic material using bacteriophage T2 virus N One group had a S-35 marked protein coat N And another had the DNA marked with P-32 N Both groups were introduced into separate bacteria cultures N After a while, the cultures were centrifuged, and the results showed that the protein coat stayed outside the bacteria, while the DNA was insidethe bacteria N This proved that DNA was the hereditary material as viruses used it to reproduce themselves via their hosts
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