Explain why enzyme replacement therapy cannot cure a genetic disease, and why gene therapy offers the only cure. What will be an ideal response?

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ANSWER: The idea that some genetic disorders could be treated began in the mid-1960s, when a cell
biologist, Christian DeDuve, proposed that symptoms of disorders caused by defective
enzymes might be improved by providing the missing enzyme. He suggested that this
procedure, called enzyme replacement therapy (ERT), could be used as a therapy for genetic
disorders.
While ERT is successful in controlling the symptoms of genetic disease, the ultimate goal is
to cure genetic diseases, and the most direct way to do this is by transferring a correct copy of
a mutant gene into the body. This approach, called gene therapy, involves the delivery of a
normal version of a mutant gene to cells in the body. Once in the cell, the expression of this
gene will produce a functional protein that restores cellular function and results in a normal
phenotype.