Genetics Flashcards
how can fetal tissue be accessed
placental - chorionic villus biopsy
skin/urine cells - amniocentesis
blood - fetal blood sampling
when can CVS be done
after 11. 5 weeks
when can amniocentesis be done
after 15 weeks
when can fetal blood sampling be done
after 18 weeks 2 pecent miscarriage risk
when can fetal dnA from maternal blood be sample
after 8 weeks
what is the disadvantage of CVS
you may have confined placental mosiciasm
Which tests analyse the whole genome
Karyotypte
Array CGH
Quantification of fetal DNA in maternal serum
Whole genome sequencing
at what stage of the the cell cycle is karyotyping done
metaphase
What tests look for targeted problems
point mutation testing
FISH
Quantitative fluorescent PCR
What kind of problem will array not show
balanced translocation
what is a polymorphism
genetic variation that is not disease causing per-se
what is a copy number variation
insertions or deletions of DNA segments - a type of polymorphism
what is a single nucleotide polymorphism
single base changes
when is fish used
when missing bit of chromosome is too small to see on karyotype - when you know what part you are looking at
when is QF-PCR used
when you know what chromosomes you want to specifically look at
when would you do array or chromosome analysis in a fetus
high risk of trisomy
fetal abnormality on scan
balance chromosomal rearrangement
what type of IUGR would worry you towards a genetic mutation
SYMMETRICAL
what can fetal dna in maternal circulation be used to find
sex determination
trisomy testin
occasionally picks up chromosome or single gene deletions
only 10 percent of the dna sampled is fetus - harder to see mutations
Why is aCGH the best genetic test in looking for downs etc
will detect small deletions
why is sex chromososne aneuploidy better tolerated eg XXX, xxy
x inactivation
what are the features of turners
webbed neck and oedema
what features occur in patau
bilateral ceft lip
postaxial polydactyly
can have cyclopia
what is a robertsonian translocation
two acrocentric chromosomes stuck end to end
what do robertsonian translocations increase the risk of
trisomy
what is aneuploidy
too many chromosomes
too few chromosomes
when is array used
deletions/duplications
when is chromosome analysis used
when you think it is a big mutation
when is next generation sequency
for very very small mutations down to 1 base pair
when can cardiac defects be seen on a scan
12-20 weeks
when can microcephaly and short limbs be seen on a scan
usually not until after 22 weeks
