Chemical abundance anticorrelations in globular cluster stars: The
  effect on cluster integrated spectra
  It is widely accepted that individual Galactic globular clusters harbor two
coeval generations of stars, the first one born with the `standard'
$\alpha$-enhanced metal mixture observed in field Halo objects, the second one
characterized by an anticorrelated CN-ONa abundance pattern overimposed on the
first generation, $\alpha$-enhanced metal mixture. We have investigated with
appropriate stellar population synthesis models how this second generation of
stars affects the integrated spectrum of a typical metal rich Galactic globular
cluster, like 47\,Tuc, focusing our analysis on the widely used Lick-type
indices. We find that the only indices appreciably affected by the abundance
anticorrelations are Ca4227, G4300, ${\rm CN_1}$, ${\rm CN_2}$ and NaD. The
age-sensitive Balmer line, Fe line and the [MgFe] indices widely used to
determine age, Fe and total metallicity of extragalactic systems are largely
insensitive to the second generation population. Enhanced He in second
generation stars affects also the Balmer line indices of the integrated
spectra, through the change of the turn off temperature and -- in the
assumption that the mass loss history of both stellar generations is the same
-- the horizontal branch morphology of the underlying isochrones.
