The HGP has enabled the rapid development of diagnostic and screening tests for genetic diseases. This is done by taking tissue samples from individuals, sometimes before birth, and characterising then analysing particular genes, looking particularly for any changes in the pattern of base pairs. Sometimes, as in sickle-cell anaemia for example, very small changes in the translation of the amino acid sequence give rise to a life-threatening malfunction.
Genetic diagnosis can be done by different techniques at three stages of life:
- before implantation, before the embryo has implanted in the wall of the uterus: this is called pre-implantation genetic diagnosis or PGD. This is a 'designer baby'.
- antenatal, during foetal life, but after implantation and formation of the placenta: this is called prenatal genetic diagnosis.
- after birth, during infancy, childhood or adult life: this is called postnatal genetic diagnosis. See pages on genetic screening.
Prenatal genetic diagnosis