Genetics Flashcards
Which tissues can be sampled to test a baby’s DNA?
Placenta- Chorionic villus biopsy
Skin/urine- Amniocentesis
Blood- Fetal blood sampling
Which test is the standard in Tayside?
Fetal DNA from maternal blood
What is confined placental mosaicism?
A discrepancy between chromosomal makeup in placenta compared to baby, ie one cell of placenta does not represent whole baby
What is the most common whole genome analysis used?
Array CGH
Disadvantage of whole genome testing?
Telling the difference between mutations (Disease causing) and polymorphisms ( Not disease causing)
How is a SNP differentiated from a mutation?
By testing the parents
Features of mutations?
De novo (But neither parent has it)
Bigger
Affects known gene
Features of polymorphism
Normal parent has it
Smaller
Empty genetic region
When are aCGH or chromosome analysis required?
High risk of trisomy
Fetal abnormality on scanning
- Structural
- Increase nuchal thickness
Prenatal screening programme in Scotland?
Dating ultrasound at 12 weeks- nuchal thickness may be seen
Serum screening at around 16 weeks- maternal bloods for downs
20 week detailed scan
What genetic management is best in structural abnormalities and why?
Amniocentesis- We want to analyse whole genome.
What genetic test is best in structural abnormalities?
aCGH- Defects may be multiple genetic causes
Also it shows small deletions
Difference between balanced and unbalanced changes?
Balanced- All chromosome material present
Unbalanced- Extra or missing chromosome material
Features of patau syndrome?
Bilateral cleft lip
Postaxial polydactyly
Holoprosencephaly
Usually miscarry or die soon
Patau syndrome genetic abnormality?
Trisomy 2013
