Finn listed two of the three steps involved in gene therapy.1. The normal allele is removed from the chromosome. 2. The normal allele is added to the cells of a person with the disorder.

First, the normal allele is removed from a chromosome. It can then be copied to make enough copies for treatment before those copies are added to the affected person’s cells. So the normal allele is copied after step 1, as choice B states.

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