2.4 antenatal and postnatal screening

Allele

Form of gene coding for a version of a characteristic

Amniocentesis

Prenatal test to assess health of foetus using cells from amniotic fluid

Anomaly Scan

Antenatal ultrasound scan performed about 20 weeks that checks for physical abnormalities

Antenatal Screening

Use of tests to identify risk of a disorder before birth

Autosome

Chromosome that is not a sex chromosome

Autosomal dominant

allele on chromosomes 1-22; always expressed in phenotype

Autosomal recessive

Allele on 1-22; expressed in phenotype if the genotype is homozygous for the recessive allele

Chorionic Villus Sampling (CVS)

Prenatal test to assess health of foetus using cells from the placenta

Dating Scan

Antenatal ultrasound scan performed about 12 weeks to determine pregnancy stage and due date

Diagnostic Tests

Tests such as amniocentesis used to confirm if the foetus has a medical condition

Embryo

Stage of development up to about 8 weeks that leads to formation of a foetus

False positive result

Error in reporting in which a test result indicates presence of a condition which is actually absent

Foetus

Stage of a baby after 8 weeks of development

Heterozygous

Having two different alleles of the same gene

Homozygous

Having two identical alleles of the same gene

Incomplete dominance

When an allele is not completely masked by a dominant allele, thus affecting an individuals phenotype

Karyotype

Display of matched chromosomes produced for medical purposes

Marker chemicals

Substances produced during pregnancy which are tested for alongside scans

Pedigree chart

Diagram showing the occurrence of phenotypes of a particular gene in a family tree

Phenylketonuria (PKU)

Metabolic disorder that is tested for by postnatal screening

Postnatal screening

Diagnostic testing of newborn babies

Prenatal diagnosis

Identification of the risk of disorders in unborn babies

Sex-linked recessive

Recessive allele carried on X chromosome