Genetics in Reproduction Flashcards
reasons for referral to genetics
• FHx of genetic condition in relatives • Diagnosis of genetic conditions – known/unknown • Management of genetic conditions • Genetic counselling o Aiding decision making o Increasing understanding
what is non-invasive prenatal testing?
Non-invasive prenatal testing (NIPT), also known as non-invasive prenatal screening (NIPS) is a new genetic test that uses cell-free circulating fetal DNA in the maternal serum to screen for the more common fetal aneuploidies: trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), trisomy 13 (Patau syndrome) and monosomy X (Turner syndrome).
what do people need to know before undergoing a genetic test?
- What a test is for/what’s the point in having it done?
- How likely is it to be positive?
- What happens if it is positive?
- What if its negative?
- What if false positive/false negative?
- Implications for other family members of positive results
- DNA stored
what is amniocentesis?
Amniocentesis is a test you may be offered during pregnancy to check if your baby has a genetic or chromosomal condition, such as Down’s, Edwards’ or Patau’s syndrome.
It involves removing and testing a small sample of cells from the amniotic fluid – the fluid that surrounds the unborn baby in the womb (uterus).
what is chorionic villus sampling?
Chorionic villus sampling (CVS) is a test you may be offered during pregnancy to check if your baby has a genetic or chromosomal condition, such as Down’s syndrome, Edwards’ syndrome or Patau’s syndrome.
It involves removing and testing a small sample of cells from the placenta (the organ linking the mother’s blood supply with her unborn baby’s).
what is preimplantation genetic diagnosis?
The term preimplantation genetic screening (PGS) refers to the set of techniques for testing whether embryos (obtained through IVF/ICSI) have abnormal chromosomes’ number. In other words, it tests if embryo is aneuploid or not
duchenne muscular dystrophy: inheritance
x linked
duchenne muscular dystrophy: screening
carrier testing
prenatal diagnosis
pre implanation diagnosis
down syndrome: screening
• Maternal age • Triple screening • CUBS screening • Selection for amniocentesis • Free foetal DNA o £500 at private clinics o Coming to NHS o Needs checked as risk of error, but negative predictive value high
common recessive disorders that raise screening issues
CF sickle cell disease thalassaemia ashkenazi jews tay-sachs disease CF W1282X BRCA1
carrier testing available by targetted testing in the UK
CF mutation analysis 80-90% sensitive UK (refer clinical genetics)
• Haemoglobinopathy MCV, Hb electrophoresis, sickledex (D/W haemoatoloy lab)
• Tay-Sachs enzyme activity (refer clinical genetics)
types of pregnancy testing:
targeted
whole population
discuss cystic fibrosis and genetic testin
1 in 2000 people are affected by CF. It is a result of defective cellular chloride transport.
Meconium ileus is a bowel obstruction that occurs when the meconium in your child’s intestine
is even thicker and stickier than normal meconium, creating a blockage in a part of the small
intestine called the ileum. Most infants with meconium ileus have a disease called cystic
fibrosis. Patients with CF suffer from recurrent lung infections. They often have pancreatic
insufficiency. Diagnosis is made on immunoreactive trypsin in first 6 weeks, sweat test and
genotyping. More than 1000 gene mutations cause disease. Some of these are particularly
common which enables genetic diagnosis, screening and prenatal diagnosis.
what is Tay-Sachs disease
Tay-Sachs is a progressive, genetic, lysosomal storage disease. Hexosaminidase A (hex-A)
deficiency results in the build-up of lipid GM(2) ganglioside especially in the nerve cells in the
brain. The baby usually develops normally until about 6 months when there is progressive
neurological deterioration. It is usually fatal by 3-5 years. 1 in 25 Ashkenazi Jews and 1 in 250
of the general population are carriers.
how is newborn screening done?
clinical exam
hearing
blood spot
