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Reproduction Week 2 2018/19 > 9: Genetics I > Flashcards

Flashcards in 9: Genetics I Deck (38)
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1

If there is a family history of inherited disease or dodgy genetic/ultrasound results in pregnancy, who should a mother be referred to?

Clinical geneticist

2

Which genetic sampling techniques for pregnancy use samples from the

a) placenta

b) amniotic fluid

c) blood?

a) Chorionic villus biopsy

b) Amniocentesis

c) Foetal / maternal blood sampling

3

Which tissues are sampled by

a) chorionic villus biopsy

b) amniocentesis

c) maternal blood sampling?

a) Placenta

b) Amniotic fluid

c) Maternal AND foetal blood

4

At what point in gestation can you do a

a) chorionic villus biopsy
b) amniocentesis
c) maternal blood sample for foetal DNA?

a) Around 11 weeks

b) 16+ weeks

c) 8+ weeks

5

What type of genetic sample is also known as non-invasive pre-natal testing?

Maternal blood sample for foetal DNA

6

When is the earliest point in gestation at non-invasive pre-natal testing can be carried out?

8 weeks

Making it very useful compared to chorionic villus biopsy and amniocentesis, which are both invasive and can only be done later in gestation

7

What is the risk involved in chorionic villus biopsy?

Miscarriage

1-2% miscarriage rate

8

Cells obtained from a chorionic villus biopsy may show different genotypes from one another.

Why?

Placental mosaicism

9

Which genetic sampling method can be carried out from around 11 weeks gestation?

Chorionic villus biopsy

10

Which genetic sampling method can be carried out from 16 weeks gestation?

Amniocentesis

11

What is the problem with amniocentesis as a genetic sampling method?

Tissue quality can be poor

12

Which genetic sampling method can be carried out from 8 weeks gestation, making it the earliest sample which can be done?

Maternal blood sample for foetal DNA

13

Taking maternal blood for foetal DNA, or non-invasive pre-natal testing, is one of the earliest and most effective tests you can do.

What's the problem with it at the moment?

Can only test for a limited number of genetic disorders

14

Which percentage of embryos have chromosomal abnormalities?

40%

But 40% of embryos don't result in miscarriage, so repair mechanisms must exist

15

Which whole genome tests are commonly used pre-natally?

Array CGH

Foetal DNA from maternal blood

Next generation sequencing (NGS)

16

Array CGH is a whole genome test used to detect (balanced / unbalanced) chromosome mutations.

unbalanced mutations

17

Which targeted tests are commonly used pre-natally?

Point mutation testing

Quantitative fluorescent PCR (QF-PCR)

18

What is the definition of a mutation?

Genetic change which causes disease

19

What is the definition of polymorphism?

Genetic change which doesn't cause disease on its own

20

How many polymorphisms does a person have on average?

3 million

21

Apart from genetic testing, how else can foetal abnormalities be discovered before birth?

Ultrasound scan

22

When are foetal ultrasound scans typically carried out?

12 weeks

20 weeks

To check for structural abnormalities suggestive of congenital disease

23

What measurement, made on foetal ultrasound, indicates whether or not a child has Down's syndrome?

Nuchal thickness

24

What is nuchal thickness?

Which disease is it used to diagnose?

Thickness of the skin on the back of a foetus's neck

Seen during foetal ultrasound

Down's syndrome

25

After seeing clear nuchal thickening on foetal ultrasound, which genetic test would you use to diagnose Down's syndrome?

Array CGH

Remember it detects extra or missing chromosomes - trisomy 21

26

Apart from array CGH, what other genetic test could you use to diagnose Down's syndrome?

Maternal blood for foetal DNA

=> Karyotype (trisomy 21)

27

What is NIPT?

Non-invasive pre-natal testing

The use of foetal DNA from a maternal blood sample to diagnose genetic disorders

28

What percentage of maternal blood contains some foetal DNA?

10%

So not a huge amount to sample

29

What is an advantage of chorionic villus biopsy or amniocentesis over NIPT?

Can test for a greater number of disorders

NIPT is currently limited to Down's syndrome

30

Which genetic disorder is commonly diagnosed using NIPT?

Down's syndrome

Occasionally you can use it for other stuff like DMD