Screening Techniques PDF - Year 11 Human Biology

Screening Year 11 Human Biology Techniques Amniocentesis  Carried out between 16th-20th week of pregnancy.  10-20ml of amniotic fluid are removed through a needle inserted through the abdomen.  Cells floating in the fluid are examined for any biochemical defects and chromosomal...

Screening Year 11 Human Biology Techniques Amniocentesis  Carried out between 16th-20th week of pregnancy.  10-20ml of amniotic fluid are removed through a needle inserted through the abdomen.  Cells floating in the fluid are examined for any biochemical defects and chromosomal abnormalities.  Involves a small risk of infection, miscarriage or damage to the foetus.  Only carried out on women thought to have a higher risk of having a child with a birth defect.  Can detect; Down syndrome, cystic fibrosis, neural tube defects (spina bifida), PKU, Tay-Sachs disease, sickle cell anemia and Duchenne’s muscular dystrophy. Amniocentesis  Chorionic villus sampling (CVS) A sample of foetal cells is collected from the chorion through a needle or catheter.  Can take place from the 9th-19th week of pregnancy.  Cellsample can then be tested for biochemical defects or chromosomal abnormalities.  Foetal tissue can be tested faster – important if the birth defect requires the termination of the pregnancy.  Disadvantages – risk of miscarriage and infection, cannot diagnose spina bifida. Chorionic Villus Sampling (CVS) Foetal blood sampling  Foetal blood directly obtainable – thin needle inserted through the abdominal wall and into the umbilical vein.  Enables quicker analysis of chromosomes.  Sample of foetal blood is extracted to detect abnormalities such as; Down syndrome, blood disorders, growth retardation and metabolic disorders. Foetal blood sampling