Polygenic traits

[Morphoeclectic]

Many traits and functions involve many genes working in tandem to produce the
desired outcome. How do the Darwinists , using Mendelian inheritance, explain
how such a arrangement of genes ( presumably mutated) could have been preserved
and extended to the point of fixation in a population?

[alextemplet]

Natural selection weeds out genes that are unsuitable to survival, and preserves genes that are favorable.