It may indicate that plant height is controlled by many genes of small effect, or by a few genes of large effect. Typically, QTLs underlie continuous traits (those traits which vary continuously, e.g. height) as opposed to discrete traits (traits that have two or several character values, e.g. red hair in humans, a recessive trait, or smooth vs ... None are dominant. Some traits are controlled by a single gene with two alleles. Name a trait like this and describe the inheritance pattern. An example of a trait controlled by a single gene and two alleles is plant height in peas. A dimpled chin is controlled by a single gene with multiple alleles and height is controlled by many genes. Some human traits are controlled by single genes with two alleles, while others by single genes with multiple alleles. Still other traits are controlled by many genes that act together. Single Genes With Two Alleles. Many human traits are controlled by a single gene with one dominant allele, and one recessive.