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Biochem 4 > Genetic Screening And Risk Assessment > Flashcards

Genetic Screening And Risk Assessment Flashcards

1
Q

What three diseases are always screened for in newborns

A
  1. Phenylketonuria
  2. Galactosemia
  3. Hypothyroidism
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2
Q

Phenylketonuria is a ______ inheritance pattern and the gene associated is ______

A 
Autosomal recessive
PAH gene (phenylalanine hydroxylase)
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3
Q

Phenylketonuria is defined by

A

The inability to digest phenylalanine, which with phenylpyruvic acid accumulate in the blood, phenylketonuria appear in the urine

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4
Q

Symptoms of untreated phenylketonuria

A
  1. Intellectual disabilities/mental retardation
  2. Seizures
  3. Tremors
  4. Hyperactivity
  5. Stunted growth
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5
Q

Why is an accumulation of phenylalanine in the blood toxic?

A

It can saturate large neutral amino acid transporters (LNAAT, LAT-1) located and the blood-brain barrier blocking important amino acids from entering (esp. tyrosine and tryptophan)

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6
Q

If phenylketonuria is untreated, irreversible intellectual disabilities occur at _____ age

A

One month of age

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7
Q

Excess phenylalanine leads to decreased tyrosine to the brain which leads to decreased production of

A

Dopamine and adrenaline

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8
Q

Phenylketonuria treatment:

A

Restriction of dietary phenylalanine (not completely)

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9
Q

What is maternal PKU

A

Mom has PKU, but eats more phenylalanine since brain has developed. Fetus affected by high phenylalanine, even without gene

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10
Q

What is PGD

A

Preimplantation genetic diagnosis

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11
Q

PGD (preimplantation genetic diagnosis) mechanism:

A

After IVF, a single cell is removed from eight-cell blastomere, PCR amplifies DNA, embryos without mutation can be implanted

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12
Q

Which prenatal diagnostic tests are invasive?

A

Amniocentesis, chorionic villus sampling (CVS), cordocentesis, preimplantation genetic diagnosis (PGD)

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13
Q

Which pregnancy screenings are non-Invasive?

A

Nuchal translucency (NT) and maternal serum screening, ultrasound, cell-free fetal DNA

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14
Q

Which pregnancy screenings test for chromosomal abnormalities

A

Amniocentesis, chorionic villus sampling (CVS), nuchal translucency (NT) and maternal serum screening, cell-free fetal DNA

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15
Q

Which pregnancy screenings have fetal loss risk

A

Amniocentesis (0.5%), chorionic villus sampling (CVS) (1%)

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16
Q

Which pregnancy screenings have no risk associated

A

Nuchal translucency (NT) and maternal serum screening, ultrasound, cell-free fetal DNA

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17
Q

Ultrasound pregnancy screening tests for

A

Structural abnormalities like neural tube defects or congenital malformations

18
Q

Gestational age =

A

The number of weeks inside the start of the last me trial period (adds roughly 2 weeks to age of fetus)

19
Q

Optimal time for amniocentesis

A

15-20 weeks

20
Q

Amniocentesis tests for

A

Cytogenetic analysis, DNA based testing, fetal a-fetoprotein (AFP)

21
Q

High AFP levels indicate significant risk for

A

Neural tube disorders

22
Q

Low AFP levels indicated significant risk of

A

Trisomies (Down Syndrome)

23
Q

Chorionic Villus Sampling (CVS) optimal time

A

10-12 weeks

24
Q

Chorionic villus sampling (CVS) sample collected

A

Fetal trophoblastic tissue (no AFP!!)

25
Q

Chorionic Villus Sampling tests for

A

Cytogenetic analysis, DNA based testing

26
Q

Ultrasound Optimal time

A

16-18 weeks

27
Q

Maternal Serum screening and Nuchal Translucency (NT) optimal time

A

11-14 weeks

28
Q

Maternal Serum screening and Nuchal Translucency (NT) sample collected

A

Maternal serum + ultra sound

29
Q

Increased nuchal translucency suggests:

A

A higher risk of chromosomal anomalies or congenital heart disease

30
Q

What makes determining high AFP levels difficult in maternal serum screening

A

Substantial overlap in maternal AFP levels between normal and Down syndrome pregnancies

31
Q

Which pregnancy screening method is beginning to replace standard maternal AFP

A

Triple screen

32
Q

Triple screen tests for which proteins

A
  1. Maternal serum (AFP)
  2. Human chorionic gonadotropin (hCG) (produced within placenta)
  3. Estriol (produced by fetus + placenta)
33
Q

Triple screen testing optimal time

A

16-18 weeks

34
Q

Triple screen drawbacks

A

Requires information about fetal number (twins, etc), many concerns with false positives

35
Q

In 95-98% of anencephaly,
MSAFP=
hCG=
Estriol=

A

MSAFP = increased

All else normal

36
Q

In 85-90% of spina bifida, MSAFP=
HCG=
Estriol=

A

MSAFP increased

All else normal

37
Q

In 60-65% of Down syndrome, MSAFP =
HCG=
Estriol =

A 
MSAFP = decreased 
HCG= increased
Estriol = decreased
38
Q

What does cell-free fetal DNA use for pre-natal screening

A

Cell-free fetal DNA that is shed into themother’s blood during pregnancy

39
Q

Can cell-free fetal DNA testing be used for all pregnancies?

A

Not for use in pregnancies with multiples

40
Q

Cell-free fetal DNA testing optimal time

A

Can be performed anytime after 10 weeks

41
Q

Which pregnancy screening method is offered to women over 35 (and not younger women due to high cost)

A

Cell-free fetal DNA

42
Q

What can cell-free fetal DNA testing detect?

A

Trisomies, aberrant numbers of sex chromosomes, sex of the baby

Biochem 4 (9 decks)

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