The law of segregation was based on work involving monohybrid crosses. A monohybrid cross is one that is carried out between parents that differ in the alleles they possess for one particular gene; one parent having two dominant alleles and the other two recessive alleles. All the offspring (the monohybrids) have one dominant allele and one recessive allele for that gene,i.e. they are hybrid at that one locus. The law of segregation can be illustrated by the example below.