Mendel's model assumes that each trait is determined by a single factor with alternate forms. We now know that this is too simplistic and that

Multiple Choice

a single gene can affect more than one trait, and traits may be affected by more than one gene.

a single gene does not produce a trait.

a single gene always affects only one trait, but traits may be affected by more than one gene.

a single trait may be affected by more than one gene.

a single gene may affect more than one trait.