Hammerling experiment - determined where cells kept hereditary material
- used Acetabularia cells, found that hereditary material in foot area
- transplanted different parts of A. mediterranea and A. crenulata
- parts eventually developed according to the hereditary material in foot area (intermediate head formed at first due to remaining RNA left in stalk)
transplantation experiments - added support that nucleus contained hereditary material
- Thomas King/Robert Briggs - transplanted nuclei from frog cells
- cells wouldn’t develop w/o nucleus
- showed that nuclei contained the information needed to direct development
- F. C. Steward - mixed fragments of carrot tissue w/ liquid growth medium
- showed that single cells can form entire, mature plants
- totipotent - containing full set of hereditary instructions
Griffith experiment - discovered transformation
- found that S. pneumoniae bacteria could only infect w/ polysaccharide coating
- dead bacteria w/ polysaccharide coating mixed w/ live bacteria w/o polysaccharide coating to form live bacteria w/ polysaccharide coating
- transformation - transfer of genetic material from one cell to another
Avery experiments - found the “transforming principle” from Griffith ’s experiments
- removed nearly all of the protein in S. pneumoniae, but transformation still occurred
- purified mixture contained elements close to that of DNA, had same density
- taking out lipids/proteins didn’t stop transformation
- DNA-digesting enzyme DNase stopped all transformations
- showed that DNA provided hereditary material for bacteria
Hershey-Chase experiment - studied bacteriophages, viruses that infect bacteria
- viruses - contain DNA or RNA surrounded by protein coat
- causes cells to produce so many viruses that it bursts (lyses)
- used radioactive isotopes to track DNA and protein coat
- showed that DNA caused changes in cells, not protein
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