Genetics

Question 1

ways to obtain tissue for DNA or chromosome test on a fetus

Answer 1

placenta - chorionic villus biopsy
skin/urine cells - amniocentesis
blood - fetal blood sampling
fetal DNA from maternal serum

Question 2

when is chorionic villus biopsy done and what is the miscarriage risk and the viability of the tissue

Answer 2

11.5 weeks
1-2%
good

Question 3

when is amniocentesis done, what is the miscarriage risk and what is the viability of the tissue

Answer 3

16 weeks +
0.5-1%
poor

Question 4

when is fatal blood sampling done, what is the miscarriage risk and what is the viability of the tissue

Answer 4

18 weeks +
1-2%
good

Question 5

when is fatal DNA from maternal blood taken, what is the miscarriage risk, what is the viability of the tissue

Answer 5

8 weeks +
none
stable

Question 6

when is aCGH or chromosome analysis done

Answer 6

high risk of chromosomal trisomy on screening

fetal abnormality on scanning such as small size, increased nuchal thickness, structural malformation

parent has balanced chromosomal rearrangement

Question 7

parental screening in scotland

Answer 7

dating US with serum biochem at 12 weeks

serum screening at 16 weeks - maternal blood test to look for biochemical markers of down syndrome

20 week detailed scan to look for other fatal abnormalities

Question 8

patau syndrome genetics

signs/symptoms

Answer 8

trisomy 13
bilateral cleft lip and post axial polydactyly
varying degrees of holoprosencephaly sometimes resulting in cyclopia

Question 9

turners syndrome signs

Answer 9

neck webbing and oedema