As in there are the class there are the fast and slow allele

As in there are the class, there are the fast and slow alleles of gluscose-6 phosphate dehydragenase (G-6-PD), which is an X-linked gene. Why produce only one type of G-6-PD enzyme? The fast allele is dominantly epistatic to the slow allele. The two alleles fail to complement each other. One of the alleles is inactivated to compensate gene dosage. One of the alleles is silenced by genomic imprinting. The fast allele is dominant to the slow allele.

Solution

The correct answer is:One of the alleles is silenced by genomic imprinting.

Reason:Only one gene is expressed while the other gene is silenced in an heterozygote condition.