In 1961 Sheldon Glashow proposed that as relation similar to the Gell-Mann–Nishijima formula for charge to isospin would also apply to the weak interaction : Q = T 3 + 1 2 Y w . Here the charge Q is related to the projection of weak isospin T 3 and the weak hypercharge Y w . Isospin and weak isospin are related to the same symmetry but for different forces. Weak isospin is the gauge symmetry of the weak interaction which connects quark and lepton doublets of left-handed particles in all generations; for example, up and down quarks, top and bottom quarks, electrons and electron neutrinos. By contrast (strong) isospin connects only up and down quarks, acts on both chiralities (left and right) and is a global (not a gauge) symmetry.