Key points from article :
CRISPR enables scientists to make very precise changes in DNA.
CRISPR technology is being used in China to treat cancer.
Doctors in Boston are planning to use CRISPR to edit cells in patients' retinas.
Victoria Gray received an infusion of billions of genetically modified cells.
Patients' cells modified with CRISPR produce a protein that is usually only made by fetuses.
Patients then undergo chemotherapy for killing the existing cells that are carrying the genetic defect.
It may take months or even years for noticing the effects on patients' health.
