2.4 antenatal and postnatal screenings

Question 1

State the purpose of ante-natal screening

Answer 1

Antenatal screening is done during pregnancy (prior to birth) to identify the risk of possible disorders within the developing embryo.

Question 2

what does antenatal screenings identify

Answer 2

This testing identifies pregnancies with a high risk of possible disorders and allows further tests and prenatal diagnosis of conditions be offered. A variety of techniques can be used to monitor the health of both mother and developing fetus.

Question 3

antenatal screening examples

Answer 3

ultrasound imaging scans
dating scans
anomaly scans
blood and urine tests

Question 4

Explain ultra sound imaging

Answer 4

Pregnant woman are given two ultrasound scans - Dating Scan and Anomaly Scan

Question 5

Explain dating scans

Answer 5

Normally takes place between 8 and 14 weeks (typically 12 weeks). This ultrasound scan is used to determine the stage of pregnancy and determine the due date

Question 6

Explain anomaly scans

Answer 6

Normally takes place between 18 and 20 weeks. This ultrasound scan is used to detect serious physical abnormalities in the fetus

Question 7

explain blood and urine tests

Answer 7

routinely carried out throughout a pregnancy to monitor the concentration of marker chemicals.

Question 8

Why is diagnostic testing used

Answer 8

Diagnostic testing techniques are used to gather cell samples that can then be cultured to produce sufficient cells to produce a karyotype to diagnose a range of genetic conditions

Question 9

What are the two main diagnostic tests

Answer 9

Amniocentesis and Chorionic Villus Sampling (CVS).

Question 10

Advantage of CVS

Answer 10

The main advantage of CVS is that it can be carried out earlier in pregnancy than amniocentesis as CVS takes the cell sample directly from the developing placenta rather than from the amniotic fluid surrounding the fetus.

Question 11

Disadvantage of cvs

Answer 11

However, this creates the main disadvantage of CVS which is that carrying out CVS carries a higher risk of miscarriage than amniocentesis.

Question 12

State what a karyotype is

Answer 12

A karyotype is a diagram constructed to shows an individual’s chromosomes arranged as homologous pairs.

Question 13

Describe how karyotypes can be used to diagnose a range of conditions

Answer 13

An individual’s karyotype can be used to identify of any genetic abnormalities when compared with a standard karyotype.

Question 14

Identify the patterns of inheritance for single gene disorders.

Answer 14

Autosomal recessive
· Autosomal dominant
· Incomplete dominance
· Sex-linked recessive

Question 15

Meaning of post natal screening

Answer 15

Post-natal screening is testing that is carried out to monitor the health of the baby after it has been born.

Question 16

Example of post-natal screening

Answer 16

One diagnostic test carried out after the baby is born is the Guthrie Heel Prick test which is used to extract blood for diagnostic testing for the condition phenylketonuria (PKU).

Question 17

Explain the cause of PKU

Answer 17

Phenylketonuria (PKU) is an inborn error of metabolism. This means that it is an inherited genetic condition. PKU is the result of a substitution mutation that results in a non-functional enzyme

Question 18

Whats the impact of PKU

Answer 18

The enzyme affected normally catalyses the conversion of phenylalanine into tyrosine. An individual with PKU must be placed on a restricted diet to limit their phenylalanine intake to minimise the harmful consequences of a build-up of phenylalanine in the metabolism of cells.