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GRIFFITH’S TRANSFORMATION EXPERIMENT

INITIAL OBSERVATIONS:. 1) Two type of Pneumococcus bacteria :. a) Smooth colonies , cells with capsule. b) Rough colonies, cells without capsule. 2) Mouse infected with capsulated bacteria get sick and die. 3) Mouse infected with non capsulated bacteria do not get sick & live.

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GRIFFITH’S TRANSFORMATION EXPERIMENT

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  1. INITIAL OBSERVATIONS: 1) Two type of Pneumococcus bacteria: a) Smooth colonies , cells with capsule b) Rough colonies, cells without capsule 2) Mouse infected with capsulated bacteria get sick and die 3) Mouse infected with non capsulated bacteria do not get sick & live 4) Mouse infected with killed smooth (capsule) strain do not get sick & live EXPERIMENTAL FINDING 5) Mouse infected with 3 & 4 (from above) did get sick and die live bacteria with capsule was found in its blood GRIFFITH’S TRANSFORMATION EXPERIMENT

  2. R cells (no capsule) produce rough colonies S cells (capsule) produce smooth colonies Avery, McLeod & McCarty made extracts from S cells Capsule material Proteins DNA RNA Rough Cells are mixed with one of the extracts from S cells Capsule material No change Proteins No change No change RNA DNA Transformation into S type Experiment of Avery, McLeod & McCarty identifies DNA as the transforming molecule

  3. labeled material found inside infected cell 32P labeled DNA Protein coat DNA PHAGE T2 35S labeled Protein coat Label remains outside Hersey-Chase Experiment Demonstrating that DNA is the genetic material for phage T2

  4. UTILIZATION OF 15N & DIFFERENTIAL CENTRIFUGATION TO STUDY REPLICATION MECHANISMS OF DNA E. coli grown in 15N Upon centrifugation DNA settles near the bottom Heavy E. coli allow to grow one generation in 14N Upon centrifugation DNA settles in the middle A second round of replicationin 14N Upon centrifugation DNA settles near the surface and in the middle Demonstration of DNA Semiconservative Replication by Meselson & Stahl

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