213 genetics Flashcards
What are the goals (5) of prenatal diagnosis?
provide informed choices
for reassurance/reduced anxiety
to allow at risk couples the ability to begin a pregnancy with the knowledge that the fetus is healthy
to give couples the option to manage/plan for pregnancy/birth/postnatal care
to enable prenatal treatment when applicable
What are the four major approaches to prenatal analysis?
genomic - karyotyping, mutation analysis
amniotic fluid - ex. alpha-fetoprotein
structural - vizualization, sonagrophy
infectious - via PCR or culture
What are indications for invasive prenatal testing (9)?
advanced maternal or paternal age
previous child with a de novo chromosome anomaly
structural chromosome abnormality in one parent (ex. balanced Robertsonian translocation)
family history of genetic disorders
risk fo neural tube defect (previous child with defect)
abnormal maternal or fetal screens
parental aneuploidy or aneuploidy mosaicism
prior child with structural birth defect
What are the three major types of invasive pre-natal diagnosis?
transcervical chorionic villus sampling
transcervical chorionic villus sampling
amniocentesis
Which type of invasive prenatal testing has highest miscarriage risk? Which is associated with placental mosaicism?
miscarriage: amniocentesis
mosaicism: CVS
What are the relative levels of alpha-fetoprotein, unconjugated estriol, beta-hCG, and inhibin A in a child with down syndrome? Trisomy 18?
down syndrome: AFP, uE3, and inhibin A low; hCG high
trisomy 18: all low
What level of pregnancy-associated plasma protein-A is associated with aneuploid pregnancies?
low levels
What does nuchal translucency indicate on fetal ultrasound?
associated with down syndrome
increased fluid space between skin and underlying soft tissue of fetal neck
What prenatal genetic tests are appropriate for a 39 year old woman?
if only screening desired: can offer carrier screening, cell-free DNA screening, MSAFP (NDT detection), ultrasound exam
if testing desired: CVS (10-14 weeks), amniocentesis (15+ weeks)
How is prenatal sonography a form of prenatal genetic testing?
it can detect anatomic features that are associated with genetic disorders or chromosome abnormalities
Which type of genomic array technology will detect trisomy 21 on amniocentesis?
both array CGH and SNP-array can identify trisomy 21, but neither can determine if it is an unbalanced translocation or not (need a karytype for this)
What is detected by an array comparative genomic hybridization (aCGH)?
detects copy number variation, cannot detect ploidy abnormalities (like triploidy)
What is detected by single nucleotide polymorphism-based arrays (SNP)?
copy number and copy neutral changes, can detect ploidy abnormalities
