Figure 4 Looped DNA structure The teal blue curved line depicts the lac operon DNA (with shading to indicate nearness to observer), which contains three possible LacIbinding sites (two of which, O 1 and O 2, are shown bound to LacI)The pseudooperator sequence O 2 is located within the lacZ gene, and the primary operator sequence O 1 overlaps the promoter sequence for the lacZYA metabolicIsotopic labeling is a technique used to track the passage of an isotope through a reaction, metabolic pathway, or cell The reactant is 'labeled' by replacing specific atoms by their isotope The reactant is then allowed to undergo the reaction The position of the isotopes in the products is measured to determine the sequence the isotopic atom followed in the reaction or the cell's metabolic pathway The nuclides used in isotopic labeling may be stable nuclides or radionuclides In the latterIt should be large, clear and with specific labels Drawings Topic 2 Cells E coli diagram labeled
