Why is it difficult to eliminate a recessive allele that expresses a detrimental trait?

It is difficult to eliminate a recessive allele that expresses a detrimental trait because the carriers are usually asymptomatic & the disease is not phenotypically expressed until it is present as a homozygous pair.

This has been one of the many challenges of Eugenics.

Explanation:

his research revealed two genetically different groups of prokaryotes, which justified splitting kingdom monera into two kingdoms. the genetic and cellular differences were so great, that these two kingdoms were eventually placed into different domains in the current three-domain system.

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