Editing Huntington's disease (section)

===Preimplantation genetic diagnosis===

[[Embryo]]s produced using [[in vitro fertilisation|''in vitro'' fertilization]] may be genetically tested for HD using [[preimplantation genetic diagnosis]]. This technique, where one or two cells are extracted from a typically 4- to 8-cell embryo and then tested for the genetic abnormality, can then be used to ensure embryos affected with HD genes are not implanted, so any offspring will not inherit the disease. Some forms of preimplantation genetic diagnosis—non-disclosure or exclusion testing—allow at-risk people to have HD-free offspring ''without'' revealing their own parental genotype, giving no information about whether they themselves are destined to develop HD. In exclusion testing, the embryo's DNA is compared with that of the parents and grandparents to avoid inheritance of the chromosomal region containing the HD gene from the affected grandparent. In nondisclosure testing, only disease-free embryos are replaced in the uterus while the parental genotype and hence parental risk for HD are never disclosed.<ref>{{cite journal | vauthors = Schulman JD, Black SH, Handyside A, Nance WE | title = Preimplantation genetic testing for Huntington disease and certain other dominantly inherited disorders | journal = Clinical Genetics | volume = 49 | issue = 2 | pages = 57–58 | date = February 1996 | pmid = 8740912 | doi = 10.1111/j.1399-0004.1996.tb04327.x | s2cid = 45703511 }}</ref><ref>{{cite journal | vauthors = Stern HJ, Harton GL, Sisson ME, Jones SL, Fallon LA, Thorsell LP, Getlinger ME, Black SH, Schulman JD | title = Non-disclosing preimplantation genetic diagnosis for Huntington disease | journal = Prenatal Diagnosis | volume = 22 | issue = 6 | pages = 503–507 | date = June 2002 | pmid = 12116316 | doi = 10.1002/pd.359 | s2cid = 33967835 }}</ref>