Disease Markers

As scientists decode the information stored in our genes, they’re learning more about the roots of disease. How many human diseases have DNA markers? Your DNA can indicate whether you have a predisposition for a certain disease. There are 30,000 genes — distinct sequences of atoms — making up the body’s DNA. Genes tell our cells to produce the proteins we need to live. Many diseases — like cystic fibrosis and sickle cell anemia — happen when a gene mutates and manufactures defective proteins. At the moment, scientists can test patients for about 500 diseases by checking for mutated genes. But, for the most part, diseases caused by a single mutated gene are very rare. And the genetic tests for more common diseases with a genetic component — say, heart disease, some cancers, autism and schizophrenia — don’t yet exist. These diseases result from the interplay of many different genes, but they’re also affected by a person’s environment. Diseases from invading viruses and bacteria might have a genetic component, too — in the sense that whether you become infected might depend on how robust your immune system is — and that heartiness or lack of it depends, in part, on your genes.


  • A resource primarily for health-care professionals, but also for people with specific questions about certain genetic diseases – Genetests
  • Ever want to see exactly where certain disease causing genes lurk? This site is a little hard to use, but you can use it to link to gene maps available elsewhere – Online Mendelian Inheritance in Man
  • Story from the NIH about cystic fibrosis

It’s probably a good idea to clarify the term “gene markers”. In the script, we used the term loosely – and focused on the question of how many human diseases are linked to genes. A more technical use of the term “gene markers” refers to sections of DNA that scientists use to hunt for disease-causing genes.

These sections of DNA may have nothing to do with causing the disease itself. But they are often associated with the disease — that is, they commonly turn up in people with a certain disease. Scientists use these markers as signposts — they assume the disease-causing gene is probably near to the marker, so the researchers scrutinize nearby genes.

Genetic mutations sometimes lead to disease — but sometimes these mutations can be helpful. For example, if a child inherits only one copy of the cystic fibrosis gene, he or she may be better able to resist the typhoid bacteria. And if a child has only one copy of the sickle cell gene, he or she is more resistant to malaria. Only some diseases, like sickle cell anemia — which warps a patient’s blood cells — occur when a person is born with a mutated copy of a single critical gene. Other diseases, like cancer, arise from the interplay of many genes.

The eruption of cancer is often influenced by environmental conditions, like a person’s diet or his exposure to harmful chemicals. And remember that genes give the blueprint for our immune system — if our genes give us a lousy one, we could be more susceptible to certain bacteria or viruses.

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