Lect 12 - Genetic Screening and Counseling Flashcards

1
Q

What is the difference between targeted and population screening?

A

Targeted screening is more specific screening in ethnic groups, possible high risk carriers, etc. Population screening is prenatal/newborn screening for common genetic disorders found in general population.

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2
Q

What are four major genetic disorders tested for prenatally?

A

1) Trisomy 21 (Down syndrome)
2) Trisomy 18 (Edward syndrome)
3) Trisomy 13 (Patau syndrome)
4) Neural tube defects

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3
Q

What are two non-invasive prenatal genetic screening modalities?

A

1) maternal serum

2) ultrasound

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4
Q

What is looked for on ultrasound to diagnose neural tube defects?

A

Nuchal translucency

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5
Q

What are two invasive prenatal genetic screens?

A

1) amniocentesis

2) Chorionic Villus sampling

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6
Q

What are the two proteins sampled for in the first trimester in the maternal serum?

A

1) PAPP-A

2) beta-hCG

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7
Q

What are the four proteins sampled for in the second trimester in the maternal serum?

A

1) alpha-fetoprotein
2) estriol
3) beta-hCG
4) inhibin A

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8
Q

What two neural tube defects is AFP increased in? What disorder is it decreased?

A

Increased in open spina bifida and anencephaly. Decreased in Down syndrome.

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9
Q

There is an increase in the amount of cfDNA (cell free DNA) or fetal DNA fragments in which genetic disorder?

A

Down Syndrome

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10
Q

What are some features seen on ultrasound in genetic disorders and what is the specific disorder it indicates?

A
Rocker bottom feet = Trisomy 18
Micrognathia = cri-du-chat
Anencephaly = Neural tube defect
Nasal bone hypoplasia = Down Syndrome
Enlarged nuchal translucency = Chromosomal aneuploidy
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11
Q

When is chorionic villus sampling done?

A

11-12 weeks

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12
Q

What genetic test is done in chorionic villus sampling?

A

FISH

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13
Q

When is amniocentesis done?

A

15-18 weeks

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14
Q

When can percutaneous umbilical blood sampling be done?

A

18 weeks

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15
Q

What are the week marks for first, second, and third trimester?

A

1) week 1-12
2) week 13-26
3) week 27-40

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16
Q

How many weeks in a full term pregnancy?

A

37-42 weeks (“normal” = 40)

17
Q

How is HbSS determined in an infant? CF? PKU? SCID?

A
HbSS = hemoglobin electrophoresis
CF = immunoreactive trypsinogen (IRT)
PKU = tandem MS
SCID = PCR for TRECs
18
Q

What are TRECs?

A

T cell receptor excision circles