Answer
- It was germline editing
- The children were not affected by a disease
- It was against ethical guidelines
- The gene editing performed was not backed up by science
- There could be off target effects
Explanation:
The uproar surrounding the use of CRISPR-Cas9 genome editing by Chinese scientist He Jiankui is that he performed what is called germline editing, which is different from editing to treat diseases such as blood diseases.
Editing cells in adults or children with diseases such as sickle cell anaemia or leukemia can prevent the faulty gene from making the individual ill, without changing the DNA in all the cells (only the affected cells). This means the edits will not be passed on to the next generation as they are not present in the sperm and eggs of the treated individuals.
Germline genome editing means he edited the embryos of humans. That means that all of the cells from the pluripotent cells in the embryo will carry the edits made by CRISPR/Cas9. This measns the affected individuals will pass the edits on to their children.
Additionally, the editing was done without the backing of proper scientific evidence. The genes the scientist chose to edit are linked to resistance to HIV, but a complete understanding of their function is lacking. Additionally, this mutation was not necessary - the children were not expected to have a debilitating disease.
The off-target effects of CRISPR/Cas9 are also not well understood. There is a concern that the Cas9 protein could start chopping up other genes in the genome (not just the ones targeted for editing).
