Prenatal Genetics

Question 1

A euploid complement of the standard diploid chromosome number; gives 69 chromosomes instead of 46

Lethal in virtually all cases

Answer 1

Triploidy

Question 2

Extra chromosome set of maternal origin
Usually has small placenta, severe growth restriction for fetus
Spontaneously aborted

Answer 2

Digynic triploidy

Question 3

Extra chromosome set of paternal origin

Enlarged placenta, partial hydatidiform mole

Answer 3

Diandric triploidy

Question 4

Not a euploid complement
Any other chromosome number that is not an exact multiple of the haploid chromosome number
Most common type of human chromosome disorder
Risk increases with maternal age

Answer 4

Aneuploidy

Question 5

Structural breakage and rearrangement of chromosome material in a different composition

Answer 5

Translocation

Question 6

Chromosome material is exchanged equally (balanced) or unequally (unbalanced)

Answer 6

Reciprocal translocation

Question 7

Short arms of two chromosomes are lost and the remaining long arms are joined

Answer 7

Robertsonian translocation

Question 8

Involves exchange of chromosome segments, not deleted or duplicated
Have a normal phenotype but have a 5-10% risk of passing on an unbalance chromosome complement to offspring

Answer 8

Balanced translocation

Question 9

Involves chromosome segments that are deleted or duplicated
Have an abnormal phenotype including birth defects, unusual facial characteristics, hearing/vision loss, mental retardation

Answer 9

Translocation

Question 10

Routine test for risk assessment of fetal down syndrome, trisomy 13, and trisomy 18
Indicated for all pregnant patients

Answer 10

First trimester screen

Question 11

Non-routine test for risk assessment of fetal down syndrome, trisomy 13 and 18 and sex chromosome abnormalities
Indicated for high risk pregnant patients

Answer 11

Cell-free fetal DNA/ Non-invasive prenatal screening (NIPS)

Question 12

Routine test for the risk assessment of Down Syndrome, Trisomy 18, neural tube defects and abdominal wall defects
Indicated for all pregnant patients

Answer 12

Maternal serum quad screen

Question 13

Samples placental chorionic villi by trans-abdominal/cervical biopsy
For increased aneuploidy risk

Answer 13

Chorionic Villus Sampling (CVS)

Question 14

Samples amniotic fluid via trans-abdominal biopsy and floating fetal cells are used for culture, chromosomal and DNA analysis

Answer 14

Amniocentesis

Question 15

Follow-up with amniocentesis culture fails or yields ambiguous results or when biochemical tests of fetal plasma or blood cells, or infection need to be confirmed
Sample of fetal blood directly from umbilical vein with ultrasound guidance or infusion of blood products

Answer 15

Cordocentesis/Percutaneous Umbilical Blood Sampling (PUBS)

Question 16

Maternal consumption of 8-10 alcoholic drinks or more per day

Answer 16

Fetal alcohol syndrome – CNS and craniofacial structure abnormalities

Question 17

SSRI’s in third trimester

Answer 17

Neonates were reported to have adverse effects, including withdrawal symptoms

Question 18

Multifactorial traits and diseases

Answer 18

Pyloric stenosis
Spina bifida
Oral clefts
Diabetes mellitus
Mental illness

Question 19

Caused by abnormal repeats of DNA within the X chromosome

Mild to profound mental retardation
Behavior abnormalities
Macrocephaly and other subtle facial characteristics
Increased risk for premature ovarian failure among females
Increased risk for adult-onset cerebellar ataxia/intention tremors

Answer 19

Fragile X syndrome