Genetic Counseling Flashcards
1
Q
Targeted screening
A
- screening of population known to be at risk (families of an affected indiv).
- screening for presymptomatic disorders in fam memb of proband (Hunt, breast canc, hemochromatosis, FAP)
- screening of high risk ethnic groups “Ashkenazi Jews”
- identifying persons at risk of having children w/ a genetic disease “carriers”
2
Q
Population screening
A
- adult screening (presymptomatic/predictive) “PAP, breast, prostate”
- screening all members of designated pop. regardless of family hx
- Prenatal screening
- Newborn screening
3
Q
Prenatal screening
A
- used to detect 3 abnormalities
- trisomy 21 and 18, neural tube defects.
- Non invasive “not diagnostic”
- Invasive “diagnostic”
4
Q
Prenatal screening: Non invasive
A
- Maternal serum screening - 16wks (look for markers participating w/ genetic disorder)
- Ultrasound - 18 wks (nuchal translucency)
5
Q
Prenatal screeing: Invasive
A
- done when there’s something from newborn screening that is predicative of a disorder
1. Amniocentesis
2. Chorionic villus sampling
6
Q
Maternal serum screening
A
- fetal DNA fragments/cell free DNA higher in women w/ DS pregnancies.
- results of T21/18 reported as risk figure not a diagnostic test.
1st trimester:
- pregnancy assoc. plasma protein-A (PAPP-A)
- B-hCG
- Nuchal translucency: high in all trisomies w/ PAPP-A decreased in all.
- B-hCG: high in T21 and low in T18/13.
2nd trimester:
- triple test: looks for 3 markers (AFP, Estriol, hCG)
- quad test: includes another marker (inhibin A).
- estriol low in all trisomies
- AFP low in all trisomies and high in NT defect.
- B-hCG: high in T21 and low in T18/13
- Inhibin A: high in T21
7
Q
AFP serum screening
A
- peak leve in 12-14 wks but detectable in fetal serum at 6 wks
- synthesized in yolk sac, fetal GIT, liver
- reduced in aneuploides “Trisomy 21”
- high in open spina bifida and even higher in anencephaly.
8
Q
Ultrasonography
A
- can detect structural abnormalities at 18wks
- micrognathia in Cri-du-Chat
- rocker bottom feet in T18
- NT defects best detected by incr. AFP + ultrasound “anencephaly”
- Enlarged nuchal translucency assoc. w/ chrom aneuploidy and Turner synd.
9
Q
Chorionic villus Sampling
A
- 11-12 wks
- removal of fetal cells by aspiration from inner surface of placenta which contains polygenetic info.
- direct chrom analysis by FISH
- risk: miscarriage/ emotional and ethical quest of termination
10
Q
Amniocentesis
A
15-18 wks
- amniotic fluid aspirated trans-abdominally
- fetal cells centrifuged and supernatant used for AFP assay.
- Risk: miscarriage and done late in gestation/ emotional and ethical quest of mid-trimester termination.
11
Q
Percutaneous umbilical blood sampling “PUBS”
A
- 18 wks of gestation
- performed in delayed suspicion of chrom abnlty; blood from umbilical cord and isolated in interphase FISH
12
Q
Prenatal Genetic counseling
A
- w/ women during pregnancy or prior to conception
- hx of infertility, miscarriages or stillbirths
- coupled older than 35 yrs
- abnl serum screen/ultrasound findings
- previous child w/ birth defect
- specific ethnicity w/ higher incidence of certain disorders.
13
Q
Preimplantation Genetics
A
- using artificial reproductive technology (ART)
- fertilizing egg w/ sperm in vitro and testing the embryo for specific condition before implanted in mother
- must know what genetic disoder looking for.
- interphase FISH test for the aneuplodies
14
Q
Newborn screening
A
- neonatal screening
- irreversible damage if disorder is untreated early in life “eg. PKU”
- early intervention is effective
- +ve test reconfirmed immediately by retesting.
- Testing is based on signs, sx or family hx.
- Tandem mass spectroscopy w/ heal pricked blood. (identifies most AA disorders)
- Electrophoresis identifies HbSS
- Immunoreactive trypsin identifies CF
15
Q
PKU
A
- newborn screening detects elevated phe in circulation
- +ve NBS confirmed by elevated phe leves via Quantitative mass spectrometry.
- management involves lifelong restriction of dietary Phe
16
Q
SC disease
A
- point mutation in B-globin = anemia
- Detection via Hb electrophoresis and DNA test (S. blot, PCR-RFLP, ASO test)
- Treatment: blood transfusions, hydroxyurea
17
Q
Thalassemia a + B
A
- AR inheritance
- detected by corpuscular Hb and Hb electrophoresis
18
Q
CF
A
- mutation in CFTR
- Detection via Immuno-reactive trypsinogen(IRT), DNA and Sweat Cl test
- Management: Abx to combat respiratory infections, gene therapy, management of assoc. malabsorption
19
Q
SCID
A
- defect which impair nl devlp of T-cells.
- SCID infancts phenotypically nl but w/ life-threatening infections w/i few months of life.
- Detection characterized by failure of T-lymphocyte dvlp and abs/low TCR excision circles (TRECs)
- TRECs are circular DNA frag generated during TCR rearrangement
- in healthy neonates, TRECs are in large numbers but barely detectable in SCID infants
- TRECs quantitated by RT-qPCR
20
Q
Carrier screening
A
- opportunity to identify couples at risk of having a child w/ a genetic disease.
- based on clinical manifestations, biochemical abnlty, specific molecular diagnostic tests or linkage analysis (in families where mutation can’t be identified)
21
Q
Genetic counseling
A
- non-directive counseling
- helping ppl understand and adapt to medical, psychological and familial implications of genetic contributions to disease.
22
Q
Autonomy
A
pt should be empowered an and allowed to make decisions themselves.
23
Q
Informed choice
A
-pt is entitled to full info about options available and potential consequences of each decision should be discussed.
24
Q
Informed consent
A
-pt is entitled to know the risks, limitations, implications & possible outcomes of each procedure
•A signed consent is usually obtained for most of the procedures
