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RDS Test 4 > B8.066 Preconceptual and Prenatal Genetic Screening and Counseling > Flashcards

B8.066 Preconceptual and Prenatal Genetic Screening and Counseling Flashcards

(54 cards)

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1
Q

prenatal

A

pertaining to the state of pregnancy at any gestational age prior to delivery

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2
Q

preconception

A

any person (men and women) with reproductive potential

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3
Q

chromosomal disorders

A

affect number or structure of chromosomes

  • Down Syndrome
  • del22q11.2 (digeorge)
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4
Q

genetic disorders

A

affect the structure and function of genes

  • cystic fibrosis
  • tay sachs
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5
Q

preconception care

A

identifiation of conditions that could affect a future pregnancy or fetus and that may be amenable to intervention

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6
Q

what is included in preconception care?

A 
family planning and pregnancy spacing
current meds
nutrition
immunization status
review of med, surg, psych history
socioeconomic, educational, and cultural context
exercise history
family history*
genetic screening/testing*
substance abuse
OB/GYN history
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7
Q

recommended genetic carrier screening

A

CF
spinal muscular atrophy
hemoglobinopathies
fragile x
genetic conditions based on eastern /central european jewish descent
genetic conditions based on founder mutations

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8
Q

recommendation for CF carrier screening

A

offer to all women who are considering pregnancy or are currently pregnant

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9
Q

which groups have the highest carrier rates of CF?

A

Ashkenazi Jewish

Non-hispanic white

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10
Q

CFTR protein

A

25 exons
250,000 bp
1480 aa
transmembrane Cl- channel > complex product

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11
Q

considerations for CF screening

A
  • populations with lower carrier frequencies also have higher rates of atypical mutations (aka easier to catch mutations in populations with more prevalence)
  • 80% of men with congenital bilateral absence of the vas deference have CFTR mutations
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12
Q

what do you do if an individual screens positive as a carrier for CF

A

DO NOT use a common mutation panel for their partner….need to do full sequencing

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13
Q

what populations are most at risk of SMA

A

caucasian
ashkenazi jewish
asian

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14
Q

what is the normal gene structure of SMA?

A

SMN1 + SMN 2 on each chromosome

SMN2 produces a functional product, but at a very low amount, doesn’t contribute much to disease process

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15
Q

most common SMA genetic mutation

A

93%
missing SMN1 on both chromosomes
due to crossing over event that excises SMN1 in each parent

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16
Q

less common SMA genetic mutation

A

6%
1 chromosome with SMN1 missing
1 chromosome with mutations that makes SMN1 nonfunctional

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17
Q

very rare SMA genetics mutation

A

1 in 1000
happens in consanguineous relationships
SMN1 on both chromosomes have mutations that make them nonfunctional

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18
Q

ways that you can be a carrier for SMA

A

carrier of deletion
carrier of mutation
2+0 carrier

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19
Q

what is a 2+0 carrier of SMA and why is this an issue

A

these people have 2 SMN1 copies on 1 chromosome and a deleted SMN1 on the other chromosome; but still technically have 2 copies
carrier screening typically only looks for # of SMN1 copies, so this person can appear to be normal on screening

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20
Q

how could you recognize a 2+0 carrier

A

look for a g.27134 T>G mutation in one of the copies

more common in african american populations

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21
Q

carrier screening recommendation for hemoglobinopathies

A

a CBC with RBC indices should be performed on all women who are currently pregnant to assess not only their risk of anemia, but also allow assessment for risk of a hemoglobinopathy
*ideally offered before pregnancy

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22
Q

B globin gene cluster

Study These Flashcards
A

chromosome 11
gamma product > contributes to Hb F
delta product > contributes to HbA2
beta product > contributes to HbA

23
Q

alpha globin gene cluster

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A

chromosome 16
zeta 1&2
alpha 1&2

24
Q

most common hemoglobinopathies

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A

sickle cell/ hemoglobin variants of the B chain
B Thalassemia
a Thalassemia

25
how do you screen for hemoglobinopathies
hemoglobin electrophoresis should be performed in addition to a CBC if there is suspicion of a hemoglobinopathy based on ethnicity (african, mediterranean, middle eastern, southeast asian, west indian)
26
what would indicated B-Thalassemia trait on CBC and Hb electrophoresis
MCV < 80 increased HbA2 (>3.5%) -indicates that not enough B chain is being made
27
what would indicated a-Thalassemia trait on CBC and Hb electrophoresis
MCV <80 | no iron deficiency
28
what do you do if you find an a or B thalassemia trait?
test partner!
29
what other lab finding would lead to testing a partner for hemoglobinopathies
clinically significant Hb variant on electrophoresis | -cant detect absence, only abnormal product
30
who should be screened for fragile x premutation
women with a family history of fragile x related disorders or intellectual disability suggestive of fragile x syndrome women with unexplained ovarian insufficiency or failure before age 40
31
CGG repeat levels in fragile x
normal : 5-44 intermediate: 45-54 (at risk for expansion only to premutation) premutation: 55-200 (increased risk for FXTAS and POF) full mutation: 201 and up (fragile x syndrome)
32
role of AGG interruption within maternal FMR1 gene
reduces the risk of offspring with fragile x
33
most common disorders in ashkenazi jewish populations
``` gaucher disease CF tay sachs familial dysautonomia canavan disease ```
34
less common, but severe disorders in the ashkenazi jewish populations
fanconi anemia niemann-pick type A bloom syndrome mucolipidosis IV
35
what are some qualifications for disorders to be selected for expanded carrier panels
carrier frequency of 1 in 100 or greater have a well defined phenotype have a detrimental effect on quality of life cause cognitive or physical impairment require surgical or medical intervention have early onset screened conditions should be able to be diagnosed prenatally should not include disorders of adult onset
36
purpose and target population of screening tests
purpose: to detect potential disease indicators target population: large numbers of asymptomatic, but potentially at risk individuals **sensitive
37
purpose and target population of diagnostic tests
purpose: to establish presence/absence of a disease target population: symptomatic individuals to establish diagnosis, or asymptomatic individuals with a positive screening test **specific
38
screening for chromosome abnormalities in the first trimester
``` nuchal translucency nasal bone ductus venosus tricuspid defects maternal serum screening ```
39
nuchal translucency testing
performed by US between 11w and 13w6d | normal is under 2.5-3 mm depending on gestational age
40
increased NT
associated with cardiac defects and chromosome abnormalities
41
nasal bone testing
screening for presence or absence only | low nasal bridge associated with some chromosome abnormalities
42
maternal serum screening in 1st trimester
PAPP-A BhCG AFP (placental, not fetal, different from AFP done in 2nd trimester to test for neural tube defects)
43
purpose of maternal serum testing in 1st trimester
adjusts risk for trisomies 18 and 21
44
components of maternal serum screening in 2nd trimester for chromosomal abnormalities
hCG AFP DIA uE3
45
how are maternal serum levels analyzed
multiples of means | normal distributions of affected and unaffected individuals
46
AFP levels in down syndrome
low
47
AFP levels in spina bifida
high
48
function of maternal serum screening in 2nd trimester for chromosomal abnormalities
performed between 15w and 22w6d correct assessment of gestational age is critical for interpretation detection for trisomy 21, 18 and neural tube defects
49
screening options for chromosome abnormalities that can be done in all trimesters
non-invasive prenatal screening may be performed anytime after 10 weeks of gestation cfDNA analyzed in fetus and mother
50
functions of screening methods for chromosome abnormalities that can be done in all trimesters
screens for trisomy 13, 18, 21 and abnormal numbers of sex chromosomes may be used to detect microdeletions (del22q11.2, cri-du-chat (5p), angelman/ prader willi, wilf hirshorn (4p), and 1p36 deletion syndrome) can screen for all chromosomes!!!
51
diagnostic testing for chromosome abnormalities and genetic disorders
amniocentesis | chorionic villus sampling
52
amniocentesis
after 15 weeks
53
chorionic villus sampling
between 10-14 weeks
54
what can fetal cells be used for after amniocentesis/ chorionic villus sampling
``` chromosome analysis microarray analysis single gene analysis analyte analysis (only amnio) WES, WGS ```

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