Although the classical Mendelian units of inheritance are easy to comprehend for categorical traits, e.g., eye color, they are probably exceptional among the many traits which determine the appearance and success of the genotype.
(the classical Mendelian units of inheritance; are; easy to comprehend for categorical traits, e.g.) (they; are probably; exceptional among the many traits) (the many traits; determine; the appearance and success of the genotype)
the classical Mendelian units of inheritance they the many traits
are are probably determine
easy to comprehend for categorical traits, e.g.
exceptional among the many traits
the appearance and success of the genotype