Antenatal Genetics and Pregnancy

Question 1

How do you genetically test the Placenta?

Answer 1

Chorionic villus biopsy at 11.5 weeks

Question 2

How do you genetically test the skin/urine cells?

Answer 2

Amniocentesis at 16+ weeks

Question 3

How do you genetically test the blood?

Answer 3

Fetal blood sampling at 18+ weeks

Question 4

When can you test fetal DNA from maternal blood?

Answer 4

8 weeks +

Question 5

What is a rather clever way of looking at chromosomes?

Answer 5

Array Comparative Genomic Hybridisation

Question 6

What is a Mutation?

Answer 6

Can be defined by a genetic change that causes disease

Question 7

What is a polymorphism?

Answer 7

Genetic variation that is not pre-se disease causing

Question 8

What are single nucleotide polymorphisms?

Answer 8

Single base changes

Question 9

What is a copy number variation?

Answer 9

Insertions or deletions of DNA segments

Question 10

Describe a Mutation?

Answer 10

De-Novo
Bigger
Affects known gene
Previously reported in same phenptype

Question 11

Describe a Polymorphism?

Answer 11

Normal parent has it
Smaller
“empty” genetic region
Previously reported as polymorphism

Question 12

What is FISH?

Answer 12

For when your missing bit of chromosome is too small to see

Question 13

When would you do aCGH or chromosomal analysis?

Answer 13

High risk of chromosomal trisomy on screening
Fetal abnormality on scanning
Parent has balanced chromosomal rearrangement

Question 14

What would count as fetal abnormality on scanning?

Answer 14

Small sized, especially if symmetrical growth failure
Increased nuchal thickness
Structural malformation - e.g. brain or heart

Question 15

How is Increased nuchal thickness screened for?

Answer 15

Ultrasound scan around 12 weeks

Question 16

What is a serum screening test at 16 weeks for?

Answer 16

Maternal blood test to look for biochemical markers of Down’s Syndrome

Question 17

In a patient where Duchenne’s Muscular Dystrophy is present in the history, what testing would you do at 10wks regarding the fetus’ sex?

Answer 17

Y present - Male - do CVS

No Y - female - reassure

Question 18

How does NIPT for Trisomy 21 work?

Answer 18

Do lots of random NGS reads

Map reads back to chromosomes

Question 19

What is NIPT?

Answer 19

Non-Invasive prenatal testing

Question 20

What is the best first genetic test for someone with potential Down’s with a Atrioventricular septal defect?

Answer 20

Array CGH

Question 21

Why is aCGH the best test?

Answer 21

Can detect small changes such as 22q11 deletion