Question

Imagine someone who has asthma has a direct-to-consumer test that tells him that he has risk- decreasing alleles for asthma in two of his relevant genes. How do you explain the fact that he has asthma, despite having two risk-decreasing alleles in relevant genes?

Answer 1

Asthma is caused by multiple interacting genes, some having a protective effect and others contributing to the disease pathogenesis, with each gene having its own tendency to be influenced by the environment.

Asthma is a what is known as a "complex" heritable disease. This means that there are a number of genes that contribute toward a person's susceptibility to a disease, and in the case of asthma, chromosomes 5, 6, 11, 14, and 12 have all been implicated.Genetic studies indicate that multiple genes are involved in the pathogenesis of this disease, and chromosomal regions likely to harbor asthma susceptibility genes have been replicated in several studies. It depends which genes are being expressed along with mixing with environmnetal factors and thus causing asthama despite having risk decreasing allels as they are not much expressed.

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