UNIT 2 - KA4
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What can a variety of techniques be used to monitor
A variety of techniques can be used to monitor the health of the mother and developing foetus
What is antenatal screening
Antenatal screening identifies the risk of a disorder so that further tests and prenatal diagnosis can be offered
All pregnant women have two routine scans using ultrasound technology:
• a dating scan • an anomaly scan
What is a dating scan
A dating scan at 8-14 weeks determines the stage of pregnancy and due date. Dating scans are used with tests for marker chemicals which vary during pregnancy
What is an anomaly scan
An anomaly scan at 18-20 weeks may detect serious physical abnormalities in the foetus
Why are routine urine and blood tests carried out throughout pregnancy
Routine urine and blood tests are carried out throughout pregnancy to monitor the concentrations of marker chemicals.
What can the marker chemicals found in routine urine and blood tests indicate
These marker chemicals may indicate a medical condition with the unborn foetus
Why should biochemical tests be synchronised with information gained from ultra sound scans
As these markers may vary in concentration during pregnancy. It is important that any biochemical tests are synchronised with information gained from ultrasound scans to minimise the risk of false positive results and false negative results
What is a false positive result
Suggesting a foetus has a condition when it does not
What is a false negative result
Suggesting a foetus has not got a condition when it does
When are further diagnostic tests which provide definitive results offered to pregnant women
• routine screening has highlighted a problem • the individual is in a high risk category (women over the age of 35) • there is a history of a harmful genetic disorder in the mothers family
Why must a risk analysis be carried out
At this point, a risk analysis must be carried out because the diagnostic tests are invasive and may in few cases, cause damage to the foetus or trigger a miscarriage
What are the two diagnostic tests
• Amniocentesis • chronic villus sampling (CVS)
What are the two screening tests
• dating scan • anomaly scan
Amniocentesis
Cells from amniocentesis can be used to make a karyotype which can detect chromosomal abnormalities
Chorionic villus sampling
CVS from the placenta can be carried out earlier in pregnancy than amniocentesis. It has a higher risk of miscarriage but CVS karyotyping can be performed on the foetal cells immediately
What are X and Y chromosomes in humans
In humans the X and Y chromosomes are the sex chromosomes
What are all chromosomes apart from sex chromosomes in humans
All others are autosomes
What can a pedigree allow
This then allows them to work out the chances of passing a genetic order on to their offspring
Allele
An alternative form of a gene
Homozygous
An individual with two identical alleles
Heterozygous
An individual with two different alleles
Genotype
The alleles which an organism carries, these are represented by letters
Phenotype
The physical appearance of an organisms genotype