Presentation on theme: "Chapter 12-1 PART I: First encounter w/ DNA. Long, long ago in the year 1928 ( about 90 years ago ) the first traces of DNA were found in a laboratory."— Presentation transcript:
Long, long ago in the year 1928 ( about 90 years ago ) the first traces of DNA were found in a laboratory setting by a British scientist named Frederick Griffith... Completely By Accident!
I. Griffith's Experiment (1928) A. At first,Griffith wanted to find a cure for a disease called pneumonia which is caused by a bacteria named Streptococcus pneumoniae B. Griffith had two different types of this bacteria growing on petri dishes in his lab : -Smooth bacteria (harmful) -Rough bacteria (harmless)
C. Experiment Step 1. Griffith injects mice w/ smooth (harmful) version of bacteria. What happens? Step 2. He injects different mice w/ rough (harmless) bacteria. What happens?
Step 3. He kills the smooth (harmful) bacteria, THEN injects the mice... Step 4. He took dead, smooth bacteria (just proven to be harmless) and mixed with rough bacteria (also harmless) and then injected that mixture into the mice... mice live! THE MICE DIE. X
Two harmless bacteria are injected into the mouse, and somehow the mouse develops pneumonia... Problem: Why is this happening?? “I hypothesize that there must be some kind of molecule – an information containing factor - that can change harmless bacteria into disease-causing ones.” - Frederick Griffith, 1928
Conclusion In other words, bacteria has the ability to pass selected traits from one organism to another. This ability would later be identified as... BACTERIA TRANSFORMATION
Experiment 1Experiment 2 Experiment 3Experiment 4 Inject mouse with ________bacteria Inject mouse with ________bacteria Inject mouse with _______________ bacteria Inject mouse with ________________ And ____________ bacteria Mouse _________ rough smooth Heat killed smooth rough Lives Dies
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