Week 4 - Genetic testing

Question 1

What is the goal of genetic testing?

Answer 1

To rule out a suspected condition, to determine the chance of the person having or passing the condiiton

Question 2

Gene test

Answer 2

Studies genes that identify mutations that lead to genetic disorder

Question 2

Chromosome test

Answer 2

Identifies changes in a chromosome, that causes a genetic condition i.e birth defect

Question 3

Protein tests

Answer 3

Studies function of the proteins, to detect for abnormalities

Question 4

PGD testing

Answer 4

Testing of pre-implantation embryo to diagnose if they are affected by a serious disorder

Question 5

Preimplantation genetic diagnosis steps

Answer 5

Cell removed from the embryo, DNA analysed

PGD determines which embryo has condition, 1-2 put back

Some embryos are frozen the ones with condition are destroyed

Question 6

ij ~~Amniocentesis\

Answer 6

15-17 weeks
Sample of amniotic fluid is sampled

Cells cultured for 2 weeks to be analysed

Miscarriage 1 in 500

Question 7

CVS

Answer 7

10-11 weeks

Samples placenta tissue

oetal cells can be directly tested:
 karyotyping;
 DNA analysis
 biochemical assay

1 in 500

Question 8

Cordoncentisis

Answer 8

Performed at 16 weeks
* Foetal blood sample obtained by inserting a fine needle into the umbilical cord
* Used to detect chromosomal abnormalities and inherited blood disorders eg sickle cell anaemia.
* Slightly higher risk than amniocentesis or CVS.

Question 9

NIPT

Answer 9

Determines if the baby has genetic abnormalities using mother’s blood

10 weeks

Pros: No miscarriage risk, high accuracy, fast turn around

Cons: Screening test not diagnostic, not suitable for triplets or above

Question 10

Maternal serum testing

Answer 10

Shows if a woman is more at risk of having a child with down syndrome pr neural tube defects, measures the protein levels in the blood

Question 11

PKU disease

Answer 11

The inability to break down the amino acid phenylalanine which can lead to a build up in the brain and cause brain damage

Question 12

PKU tetsing

Answer 12

Heel prick test

Drops of blood from baby’s heel placed on absorbent card and left to air dry

Sent to screening centre to check for high levels of phenylalanine

Question 13

Predictive vs presymptomatic testing

Answer 13

1. Identifies mutations that increase persons risk, positive means more likely to develop symptoms
2. Determines if a person will develop genetic disorder before the symptoms appear, positive means symptoms appear

Question 14

Why would someone want a presymtomatic test

Answer 14

To make the appropriate life choices, requires written consent , patient can change their mind after signing

Question 15

Positive and negative impacts of this test of presymptomatic

Answer 15

Long term physiological support,
Counselling for the child, planned medical surveillance

N: Pyschological support required