213 - Reproductive Genetics

Question 1

List 3 methods of invasive prenatal dianosis

Answer 1

• Chorionic villus sampling
  
  • aka placental biopsy
  • 10 to 13+6 weeks
• Amniocentesis
  
  • Sample of amniotic fluid
  • 15 weeks or later
• *​**
• Chordocentesis
  
  • ​Sample of fetal blood from the umbilical cord
  • Not commonly used

Question 2

Which method of invasive prenatal dianosis can be done in the first trimester?

Which can be done in the seconds?

Answer 2

• 1st = chorionic villus sampling
• 2nd = Amniocentesis

Question 3

List 4 prenatal screening tests that should be offered to a 39 year old pregnant person

Answer 3

• Carrier screening
• Cell-free DNA
  
  • Detect trisomy 21, 18, 13
• (Maternal serum alpha-fetoprotein) MSAFP
  
  • Detect neural tube defect
• Ultrasound exam
  
  • Structural malformations

Does not need cell free DNA if planning to undergo diangostic testing

Question 4

Which types of genomic array technology will detect trisomy 21 on amniocentesis?

Answer 4

Array CGH

SNP-array

However, neither method can distinguish between 3 separate copies of chromosome 21 vs. unbalanced translocation - requires visualization of the chromosome (metaphase karyotype)