Gender and Genes in Dyslexia

Since the early 1990s, a genetic link to dyslexia has been suspected. According to a research¹, about 40% to 50% of the first-degree relatives of dyslexic adults suffer from reading problems. Several other research studies support the theory that dyslexia runs in families. But which genes are responsible for this particular learning disability?

Finding the culpable genes has been the objective of many dyslexia testing and experiments. For example, in a research led by Dr. Jeffrey Gruen of the Yale School of Medicine, a mutated gene located in chromosome 6 and tagged as DCDC2 could disrupt the part of the brain that is responsible for reading. In another research led by Dr. Sylvia Paracchini of Oxford University, the gene called KIAA0319 significantly reduces a person's ability to read. This research also suggested that there are more than two dyslexic genes.

The above researches should not lead anyone to conclude that a particular case of dyslexia is due to the presence of these genes. In fact, asserting that one or two genes are the absolute causes of dyslexia would be negligent of the nature of genes and the complexity of the learning disability. To illustrate, a particular genes does not necessarily lead to a particular trait. There is no straight path from gene to trait. Genes are part of the nucleic acid that dictates the manufacture of proteins. Genes also interact with the environment, which could affect the processes of DNA transcription and replication. Thus, the presence of a dyslexic gene does not necessarily mean that a person will suffer from dyslexia.

At the same time, there are varying degrees of dyslexia in adults. There are also three different types of dyslexia. Not all of these types or the severity of dyslexia can be dictated solely by genes.

If the causes of dyslexia could not be solely attributed to genes, then what other factors can influence this learning disability? A popular answer is "gender." A research by Guinevere Eden, a neuroscientist from Georgetown University in Washington, showed that dyslexia in adults differ between men and women. Using MRI scanners, Eden discovered that dyslexia in women is characterized by a volume reduction in the right hemisphere in the brain. Dyslexia in men, on the other hand, is characterized by a reduced volume of the left brain, specifically in the left temporal lobe.

In children, there appears to be no difference in dyslexia between boys and girls. But in adults, the gender creates a significant distinction. This implies that diagnostic tests for dyslexia and the consequent treatment for dyslexia should be reevaluated, especially when dealing with adult patients.

1. Gilger, J.W., Pennington, B.F., & DeFries, J.C. (1991). Risk for reading disabilities as a function of parental history in three samples of families. Reading and Writing, 3, 205-217.