As the secrets of the human genome are revealed, we're discovering that nearly all diseases have a genetic component. Some, including many cancers, are caused by a mutation in a gene or a group of genes that occur randomly or due to exposure to some environmental factor.
In other hereditary disorders - such as Huntington's or Tay-Sachs disease - a mutated gene is passed down through a family and each generation of children can inherit the gene that causes the disease.
However, most genetic disorders are "multifactorial" being caused by a combination of small variations in genes that act in concert with environmental factors.
Many common diseases usually caused by genetic alterations in the genome - such as breast cancer and colon cancer - have also rare hereditary forms. In these cases, gene variants that cause or strongly predispose a person to these cancers run in a family and significantly increase each member's risk of developing the disease.
Having said that, how can preventive genetic testing help?
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