1.4.19 Explain the uses of genetic screening: identification of carriers, preimplantation genetic diagnosis and prenatal testing (amniocentesis and chorionic villus sampling) and discuss the implications of prenatal genetic screening.

Genetic Screening

- Newborns could be tested for a faulty allele of the CF gene, but the CF gene has many mutations and no test can cover all of them, so a negative result could be false. 

- DNA testing of adults to identify carries: a couple were both are carriers have a 1 in 4 chance of having a baby with the genetic disorder 

- If a couple have been identified as carriers yet they wish to have a baby, they might opt for prenatal screening, screening the fetus in the uterus to detect genetic defects:

1. Amniocentesis: some of the amniotic fluid is removed from the amniotic sac of the mother using a fine needle inserted in the abdomen, the fetal cells present in the amniotic fluid are obtained and their DNA is analysed and used to detect defective genes/alleles.
2. Chorionic villus sampling: cell sample from embryonic tissue is taken from the developing placenta either using a needle in the abdomen or a catheter in the vagina, the DNA from the cell is isolated and used to detect defective genes.

- Implications: risk of abortion or harm to fetus, mental and emotional issues surrounding the birth of a disabled baby, being prepared for a baby born with CF or other genetic disorders.

- Preimplantation Genetic Diagnosis (PIDG): embryos created through in vitro fertilisation (outside the body) are tested to see of they carry they faulty allele, only those which do not are implanted into the mother’s uterus.