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Flashcards in Genetics Deck (28):
1

Which organ do you carry out chorionic villus biopsy on?

The placenta

2

How could you test fetal skin cells/urine

Amniocentesis

3

How could you sample fetal blood?

Fetal blood sampling

4

When can you carry out CVS?

11.5 weeks

5

When can you carry out amniocentesis?

15 weeks

6

Earliest genetic test you can perform during pregnancy?

Fetal DNA from maternal blood (8 weeks +)
NO miscarriage risk!

7

Only genetic test with NO miscarriage risk

Fetal DNA from maternal blood

8

This test carries the risk of confined placental moscaicism

Chorionic villus biopsy

9

What are single nucleotide polymorphisms?

Single base changes

10

What are copy number variations?

Insertions or deletions of DNA segments

11

If you have a high risk of trisomy on screening, which test would you do next?

Array cGH

12

If you see a fetal abnoramlity on scanning, what test would you do next?

Array cGH

13

If a parent has a balanced chromosomal rearrangement, what test should you do?

Array CGH

14

Around what week could you see increased nuchal thickness?

Week 12

15

What is covered in the week 12 pre-natal screening?

This scan dates gestation and looks at the serum biochemistry
-done at week 12
-increased nuchal thickness may be seen

16

When is serum screening done and what does it look at?

-done week 16
-looks at maternal blood to look for biochem markers of Down syndrome

17

What does the 20 week detailed scan look at?

To look for other fetal abnormalities

18

What week could you check maternal blood for biochem markers of Down syndrome?

Week 16

19

What can you use non-invasive prenatal testing to look for?

-sex determination
-trisomy testing

(occasionally: chromosome deletions or looking at a single gene)

Non-invasive testing = maternal blood with fetal DNA in it)

20

A mother has a son with duchennes, what test can you offer?

Non-invasive prenatal testing to determine sex of the baby:
-if it is a boy do CVS (because X-linked)
-if it is a girl, reassure

21

Mrs Green is 12 weeks pregnant – serum biochemistry and nuchal thickness measurement gives a risk of 1 in 40 that the baby is affected with Down syndrome. What test can you do?

So she's already had the ultrasound
= do non-invasive prenatal testing
-test the mum's blood for fetal DNA

22

Mrs Blue comes to see you. She is 18 weeks pregnant. A detailed scan has shown that her baby has a cardiac defect: an AtrioVentricular Septal Defect that is commonly seen in Down syndrome.

Do amniocentesis and array CGH

-this is the best test for several reasons e.g. array CGH will detect small deletions such as 22q11 deletions

23

Trisomy 13

Patau syndrome

24

Patau syndrome

Tisomy 13

25

Bilateral cleft lip and postaxial polydactyl
Often varying degrees of holoprosencephayl sometimes resulting in cyclopia

Patau syndrome (trisomy 13)

26

What would array CGH look like in the parent with a balanced translocation?

aCGH would be normal (aCGH only detects imbalance)

27

Mrs Roberts comes to see you. She is 10 weeks pregnant. She has a balanced reciprocal translocation between chromosome 4 and chromosome 9, that has a high risk of causing a liveborn child with multiple malformations.
What tests would you do?

-chorionic villus sample
-direct karyotype/FISH may be available

28

When can you carry out a termination of pregnancy?

before 13 weeks = surgical
after 13 weeks = induction

There is no time limit for TOP if there is a risk of serious abnormality in the child or to the health of the mother