  The Yukawa textures of effective heterotic models are studied by using
singular spectral data. One advantage of this approach is that it is possible
to dissect the cohomologies of the bundles into smaller parts and identify the
pieces that contain the zero modes, which can potentially have non-zero Yukawa
couplings. Another advantage is the manifest relationship between the Yukawa
textures in heterotic models and local F-theory models in terms of fields
living in bulk or localized inside the 7-branes. We only work with Weierstrass
elliptically fibered Calabi-Yau manifolds here. The idea for generalizing this
approach to every elliptically fibered Calabi-Yau with rational sections is
given at the end of this paper.
