A monogenic trait is a trait produced by the effect of a gene or an allele. It is in contrast to a polygenic trait that is controlled by a polygene (multiple genes). Since the trait is produced by a single gene or allele it is less complicated compared with the trait produced by a polygene. It also follows Mendelian inheritance and therefore conforms to the set of principles such as Law of Dominance. Accordingly, the two alleles of a heterozygous pair, the allele that is expressed is the dominant allele whereas the allele that is not expressed is the recessive allele.
A mutation involving a monogene may result in a so-called monogenic disorder. It is a condition wherein a single pair of genes or a single allele is causing the disorder or the disease. There are several types of monogenic disorders. An autosomal monogenic disorder is a type of disorder involving a single gene dysfunction in the autosome. It may be dominant or recessive depending on the type of allele involved. Another type of monogenic disorder is sex-linked, which involves either X or Y chromosome.