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12.1: Identifying the Substance of Genes Investigating bacteria and pneumonia S strain: mouse dies of pneumonia R strain: mouse lives Heat-killed S strain: mouse lives Mix of heat-killed S strain and R strain: mouse dies Conclusion: some chemical factor was transferred from dead S-strain to live Rstrain cells (transformation). Offspring cells inherited the ability to cause disease chemical factor had to be a gene Repeated Griffith’s work Extracted molecules from heat-killed bacteria and treated it w/ enzymes that destroyed lipids, proteins, carbs, etc. transformation still occurred Repeated again but used enzymes that broke down nucleic acid (DNA) transformation did not occur Conclusion: DNA was the transforming factor Worked with bacteriophage (virus that infects bacteria) composed of DNA core and protein coat Grew virus cultures that contained radioactive P-32 and S-35 Proteins contain no P; DNA contains no S This will identify which molecule enters the bacteria carrying the genetic material Result: all radioactivity in bacteria was from P, the marker found in DNA Conclusion: Genetic material of bacteriophage was DNA, not protein Hershey and Chase’s experiment confirmed Avery’s findings—many scientists now convinced that DNA was the genetic material found in genes of all living cells Storing Genes control patterns of development Genes carry the info to make a flower purple Copy information information Before a cell divides it must make a complete copy of every one of its genes Transmit information DNA molecules must be carefully sorted and passed along during cell division