Hermann J. Muller (1890–1967), who was a 1946 Nobel Prize winner, coined the terms amorph, hypomorph, hypermorph, antimorph and neomorph to classify mutations based on their behaviour in various genetic situations, as well as gene interaction between themselves.
Phenotypes are compared with '>', meaning 'phenotype is more severe than' Amorphic describes a mutation that causes complete loss of gene function.
An amorphic allele elicits the same phenotype when homozygous and when heterozygous to a chromosomal deletion or deficiency that disrupts the same gene.
It is possible for an amorph to be dominant if the gene in question is required in two copies to elicit a normal phenotype (i.e. haploinsufficient).
[4][5] m/Df = m/Dp Therefore, with respect to the relationship between the original and mutated genes, one cannot talk about the effects of dominance and/or recessiveness.