Genetic Screening And Testing Flashcards
What is genetic testing
Identifying an abnormal allele of the gene in the DNA of any cell to diagnose a genetic disorder
What is amniocentesis and when is it typically performed
Involves inserting a needle into the amniotic fluid to collect fetal cells that have fallen off the placenta and the fetus.
-usually at 15-17 weeks
Cons of amniocentesis
-1% risk of causing a miscarriage
-has to be done at 15-17 weeks(have to wait for amniotic fluid to develop) when having an abortion will have large physical and emotional impact on mother
What is chorionic villus sampling and when is it typically performed
-when a small sample of placental tissue(including cells of the embryo/fetus) is removed either through the wall of the abdomen or through the vagina
-can be carried out earlier in the pregnancy at 8-12 weeks as no need to wait for amniotic fluid to develop
Con of chorionic villus sampling
-higher risk of causing a miscarriage than amniocentesis with a 1-2% risk
Pro of chorionic villus sampling
Can be performed earlier on in the pregnancy so if test gives positive result for genetic disorder it will be easier physically and emotionally for mother to have an abortion rather than having it later in the pregnancy
Pros of amniocentesis
-lower risk of miscarriage
-can test for neural tube defects which CVS cannot
What is non-invasive prenatal diagnosis(NIPD) and when it is performed
The analysis of DNA fragments in mothers blood plasma during pregnancy which contains 10-20% from the embryo
-cell-free fetal DNA is collected at 7-9 weeks depending on the genetic test to be performed
Pro of NIPD
Only requires a blood sample from mother meaning no risk of miscarriage
-can be done early on in pregnancy
Con of NIPD
Not available for all genetic conditions
-may give false positive resulting in termination of healthy pregnancy
What is testing before implantation (PGD)
Pre-implantation genetic diagnosis
-mother undergoes IVF to create embryos that can be tested before being transferred to the uterus
-remove cells from embryo and it’s DNA analysed with these results being used to decide whether to place the embryo into the uterus
Cons of pre-implantation genetic diagnosis
Expensive, sometimes stressful procedure, low success rate (30%)
Pro of pre-implantation genetic diagnosis
Avoids the need for a possible abortion so avoids the emotional and physical impact on mother of this
What is the role of a genetic counsellor
-provide advice to couples at risk of having a child with a genetic disorder
-help couple understand how disease inherited and risk that a child will have it
-explains tests available and possible courses of action depending on test outcomes