Antenatal and Postnatal Screening Flashcards
What is the function of antenatal screening?
To identify the risk of a disorder so that further tests and a prenatal diagnosis can be offered.
How many ultrasound scans are pregnant women given?
Two.
What do dating scans do?
Determine pregnancy stage and due date.
When do dating scans take place?
Between 8 and 14 weeks.
What may anomaly scan detect?
Serious physical abnormalities in the fetus.
When do anomaly scans take place?
Between 18 and 20 weeks.
Why are blood and urine test carried out during pregnancy?
To monitor the concentrations of marker chemicals.
What are examples of diagnostic testing?
Amniocentesis and Chorionic Villus Sampling (CVS).
Which diagnostic test has a higher chance of miscarriage?
Chorionic Villus Sampling (CVS).
Why is a karyotype produced from the cultured cells?
To diagnose a range of conditions.
What does a karyotype show?
An individual’s chromosomes arranged as homologous pairs.
What are the four patterns of inheritance?
- Autosomal recessive
- Autosomal dominant
- Incomplete dominance
- Sex linked recessive single gene disorders
How often is autosomal recessive inheritance expressed?
Relatively rarely
Are males and females affected differently by autosomal recessive?
No
What is the genotype of all autosomal recessive sufferers?
Homozygous recessive.
How are males and females affected by autosomal dominant inheritance?
They are affected equally.
What is the genotype of autosomal dominant non-sufferers?
Homozygous recessive.
What is the genotype of sufferers of autosomal dominant inheritance?
Homozygous dominant or heterozygous.
What is incomplete dominance?
When the dominant allele does not fully express itself.
Which sex chromosome carries more genes?
X.
What are genes which are carried on the same sex chromosome called?
Sex - linked.
What is the genotype of sufferers of sex linked traits?
Homozygous recessive.
What is the genotype of male non-sufferers?
Homozygous dominant.
How are heterozygous female carriers affected?
They don’t suffer from the condition but carry a copy of the gene which they can pass on to their offspring.
Are males and females affected differently?
Males are affected much more frequently.
Will any sons of an affected male show the trait?
No
Will any grandsons of the affected male show the trait?
Some may.
What is the purpose of Chronic Villus Sampling?
To diagnose a range of conditions like Down Syndrome.
What is the purpose of post-natal diagnostic testing?
To detect metabolic disorders like phenylketonuria.
Where are the cells used for CVS taken from?
The placenta.
Where are the cells used in amniocentesis taken from?
The amniotic fluid.
