Genetic Screening And Testing

Question 1

What is genetic testing

Answer 1

Identifying an abnormal allele of the gene in the DNA of any cell to diagnose a genetic disorder

Question 2

What is amniocentesis and when is it typically performed

Answer 2

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

Question 3

Cons of amniocentesis

Answer 3

-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

Question 4

What is chorionic villus sampling and when is it typically performed

Answer 4

-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

Question 5

Con of chorionic villus sampling

Answer 5

-higher risk of causing a miscarriage than amniocentesis with a 1-2% risk

Question 6

Pro of chorionic villus sampling

Answer 6

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

Question 7

Pros of amniocentesis

Answer 7

-lower risk of miscarriage
-can test for neural tube defects which CVS cannot

Question 8

What is non-invasive prenatal diagnosis(NIPD) and when it is performed

Answer 8

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

Question 9

Pro of NIPD

Answer 9

Only requires a blood sample from mother meaning no risk of miscarriage
-can be done early on in pregnancy

Question 10

Con of NIPD

Answer 10

Not available for all genetic conditions
-may give false positive resulting in termination of healthy pregnancy

Question 11

What is testing before implantation (PGD)

Answer 11

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

Question 12

Cons of pre-implantation genetic diagnosis

Answer 12

Expensive, sometimes stressful procedure, low success rate (30%)

Question 13

Pro of pre-implantation genetic diagnosis

Answer 13

Avoids the need for a possible abortion so avoids the emotional and physical impact on mother of this

Question 14

What is the role of a genetic counsellor

Answer 14

-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 rests available and possible courses of action depending on test outcomes