what is heterozygous truncating mutation
1 A heterozygous mutation is a mutation of only one allele. 2  A homozygous mutation is an identical mutation of both the paternal and maternal alleles. 3  Compound heterozygous mutations or a genetic compound comprises two different mutations in the paternal and maternal alleles.utations result from damage to DNA which is not repaired, errors in the process of replication, or from the insertion or deletion of segments of DNA by mobile genetic elements. Mutations may or may not produce discernible changes in the observable characteristics (phenotype) of an organism.