| Give out two classification of chromosomal abnormalities | Numerical chromosomal abnormalities
- polyploidy (triploidy, tetraploidy)
- aneuploidy (monosomy, trisomy)
Structural chromosomal abnormalities
- Balanced (the exchange or rearrangement of genetic material does not cause any missing or extragenetic information)
- Unbalanced (the structural chromosomal changes cause missing or extra genetic information) |
| Name three autosomal trisomies that are viable during pregnancy | Down Syndrome
- trisomy 21
Edwards's syndrome
- trisomy 18
Patau syndrome
- trisomy 13 |
| Aneuploidy of the sex chromosomes is relatively common.
Name common syndromes caused by aneuploidy | Turners syndrome
- 45,X
Triple X syndrome
- 47,XXX
Klinefelter syndrome
- 47,XXY and 47, XYY |
| Give the terms used for chromosome mutations within one chromosome and give definitions to those terms | Deletion
- Loss of genetic material
Duplication
- some genetic material doubled
Inversion
- No loss of genetic material, but rearrangement of genetic material |
| What is the purpose of amniocentesis | Prenatal diagnostic of chromosomal abnormalities and to determine foetal infections |
| Describe the basic procedure of amniocentesis | Small amount of amniotic fluid is removed from amniotic sac
- under ultrasound guidance
- foetus between 15-20th weeks
- Syringe through skin, fascia, uterine wall, and amniotic cavity at 90 degrees |
| How is chorionic fluid sampling different to amniocentesis | Instead of sampling amniotic fluid, sample of chorionic villus (placenta tissue) is taken for testing
Placenta-highly vascular organ
- allows nutrient uptake
- gas exchange
- homeostasis
of developing foetus
Transcervical or transabdominal approach depeding on the position of the placenta
carried out during 10-12th weeks of gestation |
| Difference between screening and testing | Screening
- applied on whole population
- large number of asymptomatic, but potentially at risk individuals
Testing
- applied to either symptomatic individuals to establish diagnosis
or
- asymptomatic individuals with a positive screening test |
| Name six antenatal and newborn programmes in England | - sickle cell and thalassemia
- fetal anomaly (downs, patau, edwards)
- infectious diseases in pregnancy
- newborn and infant physical examination
- newborn blood spot (e.g. PKU, SCD, CF, CHT)
- newborn hearing screening |
| Give out requirements for diagnostic tests | Parental and sibling DNA samples
- blood or saliva
DNA from foetus
- isolated from amniotic fluid or chorionic villus biopsy, or from mother's blood |
