Genetic Condition, Pregnancy, Birth defects and Genetics
Every child receive chromosomes from your mother and father and with them the genes that make up your genetic code. A genetic condition is due to a mistake or mutation in the genetic code on a chromosome. In addition, the gene can be passed from parent to child. An example of a genetic condition is sickle-cell anaemia, in which there is an abnormality in the gene controlling the formation of the red blood cells that carry oxygen around the body.
Thalassaemia is another genetic condition in which there is an abnormality in the gene controlling the production of red blood cells, leading to varying degrees of anaemia. Another example of a genetic condition is cystic fibrosis, in which the mucus produced by the lungs is abnormally thick and difficult to clear, leading to recurrent chest infections. In this condition there is also abnormality of the pancreas, affecting its ability to produce enzymes to break down food in the gut and thus leading to malabsorption of food.
Some genetic conditions are dominant , others are recessive. Sickle-cell anaemia, like cystic fibrosis, is a so-called ' recessive ' condition because for a baby to be affected it needs to inherit two sickle-cell genes , one from each parent.
Each parent will pass the gene to the child at conception. If one parent pa s se s on the sickle-cell gene and the other passes on a normal gene, this is not sufficient to cause the condition. To pass on the two sickle-cell genes necessary to produce the disease each parent will have to be either affected by the disease or be a carrier of it. A carrier has one normal gene and one abnormal gene. Carriers do not usually have the disease, but have the potential to pass this gene on to a child. They are unlikely to know that they have the gene unless there is a family history of the disease.
Occasionally the abnormal gene can be dominant , however, as in the case of brittle bone disease and Huntingtons chorea in which brain cells degenerate, leading to jerky, involuntary movements and progressive dementia. This means that if the baby has one abnormal gene it will be affected even if the other gene is normal. In dominant conditions only one parent need carry and pass on the gene.
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