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PoM > Genetics - Genetic Testing > Flashcards

Genetics - Genetic Testing Flashcards

1
Q

What happens at 10-14 weeks into the pregnancy?

A

Nuchal scan

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2
Q

What is involved in a nuchal scan?

A

Variety of blood tests and nuchal translucency tests

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3
Q

What do we assess the risk of with a nuchal translucency?

A

Downs

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4
Q

What is the main purpose of a nuchal scan?

A 
Detects for multiple pregnancy
Dates the pregnancy
Detects for early miscarriage
Detects for major foetal abnormalities
Detects for Downs
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5
Q

When is the next scan after the nuchal scan?

A

Mid trimester - 20-22 weeks

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6
Q

What is the purpose of a mid trimester anomaly scan?

A

More detailed normal scan - looks at brain, spinal cord, bones, heart face, kindeys

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7
Q

How many conditions do we look for with a mid trimester anomaly scan?

A

11

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8
Q

How do we gauge the risk for Down’s in an NT?

A

Increased thickness of back of neck (above 3mm)

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9
Q

What are we measuring in an NT?

A

Thickness at back of neck

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10
Q

What is NT not used for?

A

Not diagnostic - screening purposes only

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11
Q

When do we arrange pre natal testing?

A

Following abnormalities on normal scans
Combined risk of Downs
Parents have good reason to arrange e.g. family history

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12
Q

What are the main aims of prenatal testing?

A

Inform parents of affected baby

Prepare for complications before or after birth

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13
Q

What does prenatal testing allow for?

A

Termination of foetus

Management of pregnancy around the disease

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14
Q

What can a foetal MRI be used for?

A

Further testing or clarification

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15
Q

What can we use to diagnose any cardiac conditions?

A

Foetal cardiac scan

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16
Q

Aside from NT, what else can we use to detect for the risk of trisomy 21/18 or neural tube defects

A

Maternal serum testing markers in then blood

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17
Q

What is the neural tube

A

Precursor to CNS

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18
Q

What are the two non invasive methods of prenatal testing?

A

Maternal blood tests

cell free foetal DNA (cffDNA)

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19
Q

What is cell free foetal DNA?

A

Where fragments of foetal DNA are shed from the placenta and enter the mother’s blood stream

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20
Q

When is the earliest that cffDNA can be detected in the blood

A

4-5 weeks

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21
Q

Why do we not test for cffDNA at its earliest point that it appears?

A

Cannot be tested until around 9 weeks when results are most accurate.

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22
Q

What is NIPD?

A

Non invasive prenatal diagnosis

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23
Q

What NIPDs can we get from cffDNA?

A

Achondroplasia
Thanatophoric dysplasia
Apert syndrome

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24
Q

What non disease can we use NIPD for?

A

Sexing - SRY gene on the Y chromosome of boys can be detected

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25
Q

How much do NIPD cost?

A

Free on NHS

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26
Q

Can we diagnose with NIPT?

A

No

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27
Q

What do we do if we find anomalies with NIPT?

A

Arrange invasive testing

28
Q

How are multiple pregnancies a limitation with NIPT/D?

A

We do not know which child is affected or whether both are affected

29
Q

How is women with a high BMI a limitation with NIPT/D?

A

They will have overall more of their own cell free DNA in the blood

30
Q

What are some of the benefits of NIPT/D?

A

Non invasive
No risk of miscarriage
No specialist required
Can be offered earlier than most invasive tests

31
Q

When is invasive testing offered?

A

When there is a known risk of a disease or there is abnormal results from normal scans/ NIPT

32
Q

What are the two main invasive testing methods?

A

Chorionic Villus Sampling

Amniocentesis

33
Q

What do invasive tests include?

A

Include molecules, cytogenic and biochemical tests

34
Q

How is invasive testing offered?

A

Outpatient bases

35
Q

When is CVS carried out?

A

11-14 weeks

36
Q

What is the risk of a miscarriage with CVS?

A

1-2%

37
Q

How is a CVS sample taken?

A

Sample of chorionic villus is taken via the transvaginal or trans abdominal route

38
Q

What is the main benefit of CVS?

A

Allows the patient to get earlier results than amniocentesis - important for ToP decisions.

39
Q

What is amniocentesis?

A

Insertion of a needle into amniotic sac and taking a sample of the fluid

40
Q

When is amniocentesis carried out?

A

15-16 weeks

41
Q

What is the miscarriage risk of amniocentesis?

A

up to 1%

42
Q

What is another risk of amniocentesis?

A

Risk of infection or Rh sensitisation

43
Q

What tests do we carry out with an obtained DNA sample?

A
  • Testing for the disorder in question
  • Karyotyping
  • QF-PCR
44
Q

What is the purpose of testing for the disorder in question?

A

We want to see if the foetus is a carrier or whether they are affected/unaffected

45
Q

What is the purpose of karyotyping?

A

If parents are affected by translocation, there is a chance that the foetus will also be affected

46
Q

What is the purpose of QF-PCR

A

Carried out for all - looks for trisomy of 13, 18 and 21

47
Q

What is a CGH array?

A

Detects imbalances on all of the chromosomes and will be able to detect for micro deletions or duplications

48
Q

When is a CGH array offered?

A

After anomalies on 20 week scan

49
Q

What happens if abnormalities are shown on a CGH array?

A

We will test the parents to see if the abnormality is inherited or if the foetus is the first affected family member.

50
Q

What is trio-exome?

A

Prenatal exome testing

51
Q

What is the exome?

A

Coding region of a genome

52
Q

What does trio-exome allow us to do?

A

allows us to look at the baby’s exome if there are significant abnormalities

53
Q

What do we sequence in tiro-exome?

A

Exons not introns

54
Q

When there is a known reproductive risk, what options do parents have?

A 
Conceive naturally 
Use egg/sperm donor
Adoption
Choose not to have children 
PGD
55
Q

What is PGD?

A

Pre-implantation genetic diagnosis (IVF with additional step to test embryo before implantation)

56
Q

What is step 1 of PGD?

A

Stimulation of ovaries

57
Q

What is step 2 of PGD?

A

Egg collection

58
Q

What is step 3 of PGD?

A

Insemination in lab

59
Q

What is step 4 of PGD?

A

Fertilisation

60
Q

What is step 5 of PGD?

A

Embryo biopsy

61
Q

What is step 6 of PGD?

A

Embryo testing

62
Q

What is step 7 of PGD?

A

Embryo transfer (if embryo test is ok)

63
Q

What is step 8 of PGD?

A

Pregnancy test

64
Q

What is ICSI?

A

Intracytoplasmic Sperm Injection - avoid complications generate by letting sperm compete for the egg

65
Q

When do we use PGD?

A

Used for genetic conditions e.g. Huntington’s DMD susceptibility.

66
Q

What are some of the criteria for PGD?

A

Non smokers
Stable relationship
Mother is maximum 39 years old

67
Q

What may decision making depend upon?

A

Previous experience
Family situation
Personal/cultural beliefs

PoM (27 decks)

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