Practice question

Failure to complement occurs when trans heterozygote inherits two different recessive mutations within same gene leaving no wild-type coding sequence to produce active product. Chromosome one carries lesion a1 with functional domain disrupted, chromosome two carries lesion a2 in same cistron so both polypeptides defective and enzymatic activity absent. Auxotrophy or phenotypic abnormality persists and phenotype stays mutant. This non-complementation defines allelism indicating mutations represent different alleles of single locus even if nucleotide changes differ, grouping into one complementation group functionally.