Seymour Benzer used phage T4 mutants, Experimental
evidence that a gene is a linear sequence of nucleotide pairs. Some regions of
chromosomes have "hot spots" for mutations. Benzer's experimental
approach to fine structure mapping of the rII locus. Generated 1612 spontaneous point mutations
and several deletions in rII locus identified two complementation groups, rIIA
and rIIB. Mapped locations of deletions
relative to each other using recombination.
Mapped locations of point mutations relative to the deletions. Tested
for recombination between all point mutations within the same complementation
group.
Mario sets up an experiment to determine the source of the oxygen gas produced by photosynthesis. To determine this, he uses an isotope of oxygen called O-18. He labels the O-18 oxygen so he can follow its path through photosynthesis. Plant A is given carbon dioxide that contains the O-18 isotope. Plant B is given water that contains the O-18 isotope. When he examines the oxygen from both plants, only plant B produced O-18 oxygen. This indicates that the source of oxygen is water. The photosynthesis involves the transfer of electrons between the photosystem I and II. The water gets split into oxygen, hydrogen ions and electrons in the photosystem I. The electrons move to the photosystem II where the carbon fixation into sugars takes place. The plant A will have O-18 isotope in its synthesised sugar molecule, which gets stored inside it.
