The DNA in the zebrafish was deleted, and the human version was inserted later, without affecting the main DNA (probably using a “plasmid”).
Without the human DNA “insert”, there was a developmental defect. with either the human DNA insert or the original zebrafish DNA (as an insert), there was no developmental defect, leading to the conclusion that the human version is functionally equivalent to the zebrafish version.
There are several complications addressed in the article, which I did not describe. Anyway, using a “control vector” is considered trivial, and I believe they checked this.
The DNA in the zebrafish was deleted, and the human version was inserted later, without affecting the main DNA (probably using a “plasmid”). Without the human DNA “insert”, there was a developmental defect. with either the human DNA insert or the original zebrafish DNA (as an insert), there was no developmental defect, leading to the conclusion that the human version is functionally equivalent to the zebrafish version.
How do we know whether, by replacing the insert with a random sequence of base pairs the same length, there would be no developmental defect either?
There are several complications addressed in the article, which I did not describe. Anyway, using a “control vector” is considered trivial, and I believe they checked this.