GENETIC DISORDERS AND ANTENATAL CARE
Dominant and recessive genes
Every cell in the human body contains twenty-three pairs of matching chromosomes, which carry the genetic blueprint determining every human characteristic. Each gene on each chromosome has its corresponding gene on the matching chromosome. One gene is usually dominant over the other, and is expressed as a certain characteristic. Only if a recessive, or weaker, gene is present on both chromosomes in a pair will the characteristic it represents be expressed. The twenty-third pair of chromosomes determines the baby’s sex. Females have two large X chromosomes, whereas males have a large X and a smaller Y chromosome.
Chorionic villus biopsy
This recently developed test is used to test for specific genetic abnormalities, such as cystic fibrosis. It can be performed earlier than amniocentesis, but does carry a greater risk of causing a miscarriage. The procedure is similar to amniocentesis, but instead of removing a small amount of fluid, several cells are removed from the developing placenta for testing. If you have a family history of certain hereditary disorders, your doctor will let you know if it is advisable for you to have this procedure performed.
Foetoscopy
This is a procedure in which a fibreoptic instrument, a needle with a tiny camera attached to it, is passed into the womb to inspect the foetus.
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