Genetics Flashcards
What is the name given to trisomy 13?
What is the likelihood that the meiotic error leading to trisomy 13 is maternal?
- Trisomy 13 is Patau’s syndrome.
- The meiotic error in Patau’s syndrome is maternal 85% of the time.
What is the name given to trisomy 18?
What is the likelihood that the meiotic error leading to trisomy 18 is maternal?
- Trisomy 18 is Edward’s syndrome.
- The meiotic error in Edward’s syndrome is maternal 90% of the time.
What is the name given to trisomy 21?
What is the likelihood that the meiotic error leading to trisomy 21 is maternal?
- Trisomy 21 is Down’s syndrome.
- The meiotic error in Down’s syndrome is maternal 85% of the time.
What is the name given to 45,X?
What is the likelihood that the meiotic error leading to trisomy 45,X is maternal?
- 45,X is Turner’s syndrome.
- The meiotic error in Turner’s syndrome is maternal 20% of the time.
What is the name given to 47,XXX?
What is the likelihood that the meiotic error leading to trisomy 45,X is maternal?
- 47,XXX is Triple X syndrome.
- The meiotic error in Triple X syndrome is maternal 95% of the time.
What is the name given to 47,XXY?
What is the likelihood that the meiotic error leading to trisomy 45,X is maternal?
- 47,XXY is Klinefelter’s syndrome.
- The meiotic error in Klinefelter’s syndrome is maternal 55% of the time.
What is the name given to 47,XYY?
What is the likelihood that the meiotic error leading to trisomy 45,X is maternal?
- 47,XYY is just 47,XYY syndrome.
- The meiotic error in 47,XYY syndrome is never maternal.
What is the difference between prenatal diagnosis and preimplantation diagnosis?
- Prenatal diagnosis is done from samples in vivo, e.g. from the mother’s blood (NIPT), amniocentesis, chorionic villus sampling etc.
- Preimplantation diagnosis is done from a blastocyst produced from IVF or ICSI before artificial implantation.
What is the difference between the 12-week ultrasound can and the 20-week ultrasound scan?
- The 12-week ‘dating’ scan is to check foetal development.
- The 20-week ‘anomaly’ scan is to check for structural anomalies.
When is chorionic villus sampling (CVS) done?
- A chorionic villus sampling is done if another scan indicates that there may be a genetic defect.
- It is done from 11 weeks of gestation.
When is an amniocentesis done?
Give one advantage and one disadvantage of using amniocentesis of chorionic villus sampling.
- An amniocentesis is done if another scan indicated that there may be a genetic defect.
- It is done from 15 weeks of gestation.
- Amniocentesis is safer than chorionic villus sampling, but can only be done later - this is important if the couple decide to abort the foetus.
At which stage during gestation can non-invasive prenatal testing (NIPT - using a sample from the mother’s blood) be done?
When is non-invasive prenatal testing (NIPT - using a sample from the mother’s blood) not appropriate?
- Non-invasive prenatal diagnosis can be done from 8 weeks gestation.
- Non-invasive prenatal diagnosis is not appropriate when the disease shows a recessive inheritance pattern, as the mother could be a carrier.