Prenatal Testing Flashcards
What is measured in the 11-13 week screening ultrasound?
Nuchal translucency > indicative of pathology is thickened
Crown rump length > dating
When do you get a phenotype with balanced translocations?
When the translocation site disrupts an important gene
What is the difference between a balanced and unbalanced chromosome translocation?
In the balanced there is no net gain or loss of genetic material while there is in unbalanced
What are the limitations of sampling free fetal DNA in maternal blood?
Expensive
Needs to be confirmed with further tests
Is genetic screening for carries covered my medicare?
No
What can microarrays detect?
SNPs
Chromosomal numbers
Copy number variations
What is one abnormality that chromosome microarray can’t detect that karyotyping can?
Chromosome translocations
The risk of which disease is associated with increasing age of the father?
Achrondroplasia
What percentage of babies are born with a birth defect in Australia?
~4%
What is performed if a neural tube defect is detected in the 2nd trimester screening?
A diagnostic ultrasound
What are the main conditions that prenatal screening targets?
Trisomys - 21, 18
Neural tube defects
Genetic carrier state
What might a region of homozygosity in a molecular karyotype indicate?
Autosomal recessive disorder
Consanguinity
Which is more risky, chorioninc villus sampling or aminocentesis?
Chorionic villus sample (1% vs 0.5% risk of miscarriage)
What does this karyotype mean: 46 XY der (14:21)+21?
There is an extra chromosome 21 translocated on one of the chromosome 14s
What is the advantage of FISH vs karyotyping?
It can be performed on non-dividing cells therefore the results can be attained within 24 hours compared to around 2 weeks for karyotyping.
However it is more expensive and less definitive
