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Block 1 - Week 3 > Genetic and Prenatal Testing > Flashcards

Genetic and Prenatal Testing Flashcards

1
Q

What are the two types of prenatal genetic testing?

A

Screening tests and diagnostic tests

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2
Q

What do prenatal screening tests do?

A

Estimate chances that a fetus has an aneuploidy or other disorder

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3
Q

What are the main prenatal screening tests?

A 
First Trimester Screen (Mother)
Triple Screen (MSAFP)
Quad Screen (Mother)
Carrier Screening (Mother and/or Father)
Cell-Free DNA Testing (Fetus)
Ultrasound (both screening and diagnostic)
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4
Q

What do prenatal diagnostic tests do?

A

Confirm if a fetus actually has a certain disorder

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5
Q

What are the main prenatal diagnostic tests?

A 
Amniocentesis
Chorionic Villus Sampling (CVS)
Percutaneous umbilical blood sampling
Preimplantation genetic diagnosis
Ultrasound (both screening and diagnostic)

These tests use cells from the fetus or placenta

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6
Q

First Trimester Screen

A

11-14 weeks (1st Trimester)
Screens for trisomy 13, 18, and 21
Measures nuchal translucency (via US) and B-hCG and PAPP-A (via maternal serum)

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7
Q

First Trimester Screen Interpretations

A

Trisomy 21: increased NT, increased B-hCG, decreased PAPP-A

Trisomy 13 and 18: increased NT, decreased B-hCG, and decreased PAPP-A

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8
Q

Triple Screen

A

15-20 weeks (2nd Trimester)
Screens for trisomy 13, 18, 21, and NT defects
Measures maternal serum for MSAFP + uE3 + hCG

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9
Q

Quad Screen

A

Same as triple screen + checks for inhibin A

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10
Q

Triple Screen Interpretation

A

Trisomy 21: decreased MSAFP, decreased uE3, increased hCG

Trisomy 13 and 18: decrease in –> MSAFP, uE3, hCG

Nural tube defect (NTD): Large increase in MSAFP

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11
Q

What does MSAFP stand for?

A

maternal serum alpha-fetoprotein

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12
Q

What does uE3 stand for?

A

unconjugated estriol

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13
Q

What does hCG stand for?

A

Human chorionic gonadotropin

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14
Q

What does NTD stand for?

A

Nural tube defect

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15
Q

What does NT stand for?

A

Nuchal translucency

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16
Q

Cell-Free DNA

A

After 10 weeks of gestation, circulating free DNA (cfDNA) are released from placenta into maternal circulation. Can be used to screen for trisomy 13, 18, and 21 using next generation sequencing

Also called NIPT or NIPS: Non-Invasive Prenatal Testing/Screening

17
Q

Ultrasound

A

20 weeks

Screens for anatomical alterations and NTDs

18
Q

Chorionic Villus Sampling

A

10-13 weeks
Biopsy of the chorionic villi of placenta
Chromosome analysis (aneuploidy, translocations, deletions, duplications, single-gene disorders)
Miscarriage risk slightly higher than amniocentesis

19
Q

Amniocentesis

A

16-20 weeks
Needle obtains amniotic fluid which contains cells of fetal origin which can be used for karyotype, FISH, comparative microarray analysis.
Risks infection and miscarriage

20
Q

Preimplantation genetic diagnosis (PGD)

A

~5 trophectoderm cells removed from blastocyte-stage embryo (5-6 days)
For in vitro fertilization

21
Q

Percutaneous umbilical blood sampling

A

At or after 18 weeks
Sample of feta blood withdrawn from umbilical cord
Rarely used, has been largely replaced by other methods

22
Q

What does PAPP-A stand for?

A

Pregnancy-associated plasma protein A

23
Q

What can Karyotyping test for?

A

Aneuploidy + Large CNV

24
Q

What does CNV stand for?

A

Copy number variant; when the number of copies of a particular gene varies from one individual to the next

25
Q

What can FISH test for?

A

Aneuploidy + Large CNV + Small CNV

26
Q

What can chromosomal microarray test for?

A

Aneuploidy + Large CNV + Small CNV

27
Q

What can next gen sequencing and targeted sequencing test for?

A

Aneuploidy + Large CNV + Small CNV + single-gene variant

28
Q

Single gene sequencing

A

Helps to identify a single gene or short list of genes pertaining to a suspected syndrome

Good for identifiable symptoms or known family history

29
Q

Phenotype specific panel testing

A

Tests for a group of genes related to phenotypes

Good for when an identifiable group of features is present but not easily specific to one particular syndrome or gene

30
Q

Whole-Exom Sequencing (WES)

A

Gives data on all protein-coding regions of the genome

31
Q

Whole-Genome Sequencing (WGS)

A

Gives data on entire genome

32
Q

When are the different trimesters?

A

First trimester: weeks 1-12

Second trimester: weeks 12-26

Third trimester: weeks 27 until the end of pregnancy

Block 1 - Week 3 (7 decks)

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