Genetics Flashcards
How is the 1st trimester trisomy screen carried out?
Carried out by serum markers (PAPP-A, hCG) and nuchal thickness scan
What does a nuchal scan test for?
measures the nuchal fold thickness. This is an area of tissue at the back of an unborn baby’s neck.
Measuring this thickness helps assess the risk for Down syndrome and other genetic problems in the baby.
32 year old woman has a booking appointment with her midwife at approximately 8 weeks gestation. Which foetal genetic disorders can be screened for?
Trisomy 13 (Patau syndrome)
Trisomy 18 (Edwards syndrome)
Trisomy 21 (Down syndrome)
NIPT has a positive predictive value of >90%. true/false?
True
What is a CVS?
Chorionic villus sampling is a form of prenatal diagnosis done to determine chromosomal or genetic disorders in the foetus.
It entails sampling of the chorionic villus and testing it for chromosomal abnormalities, usually with FISH or PCR.
Taken between 11-14 weeks gestation
What is amniocentesis?
Amniocentesis is done to remove amniotic fluid and cells from the uterus for testing or treatment.
Carried out >15 week gestation
Reasons for doing amniocentesis?
Genetic testing, diagnosis of foetal information, treatment (to drain excess amniotic fluid from uterus due to polyhydramnios) or foetal lung testing
What is genetic amniocentesis?
Genetic amniocentesis can provide information about the baby’s genes.
Genetic amniocentesis is usually done between weeks 14 and 20 of pregnancy.
Amniocentesis done before week 14 of pregnancy might lead to more complications.
Reasons for genetic amniocentesis?
Having positive results from a prenatal screening test.
Having an earlier pregnancy affected by a genetic condition.
Being 35 or older.
Having a family history of a genetic condition, or if the parents are carriers of a genetic condition.
Having unusual ultrasound findings.
What is chromosome microarray (CMA)?
a powerful diagnostic tool that is used to identify genetic causes of illness and developmental problems.
CMA only tests for variations in DNA copy number. It can identify:
large deletions and microdeletions and large duplications and microduplications
most abnormalities of chromosome number (eg Down syndrome)
unbalanced rearrangements of chromosome (eg complex insertions or deletions).
Chromosome Microarray has higher resolution but only detects imbalance
true/false?
True
What can CMA NOT detect?
does not identify:
single gene mutations
fragile X syndrome (FXS)
balanced rearrangements (eg: translocations and inversions).
So can only detect chromosomal shifts
What is mutation (Pathogenic variant)?
Can be defined as a genetic change that causes disease
What is polymorphism (Benign variant)?
Genetic Variation that isn’t exactly disease causing
Pregnant woman diagnosed with trisomy 21 at 28 weeks gestation. What is first line medication?
Potassium chloride injection