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Chromosomes and Disabilities
By Alan Harchik, Ph.D., BCBA

What causes developmental disabilities in children? This is a question parents and professionals often ask. Some disabilities appear to be due to chromosome or gene disorders. Learning more about these types of disorders may lead to better prevention, and can help couples make decisions when they are planning to start a family.

Chromosomes and genes are in every cell of our body. In every cell, we have 46 chromosomes that occur in 23 pairs. One of each pair came from each of our parents. Chromosomes contain genes that instruct our body to grow, develop, and function. It is estimated that there are more than 20,000 genes in every cell.

Sometimes part of a chromosome is missing or duplicated. Other times, parts of the chromosome stick together or get rearranged in the wrong order. As a result, genes are missing, altered, or deformed. This may result in a medical condition or a learning problem. Sometimes there is no obvious impairment.

Scientists are conducting more and more chromosomal and genetic research to (1) identify the chromosome and gene irregularities that occur in children with specific disabilities, (2) explore what causes the irregularities, and (3) examine best treatments for these children.

Genetic Disorders and Their Causes
Researchers have identified specific chromosome or genetic problems for a number of developmental and cognitive disabilities. At May Institute, we support individuals with these disabilities in our programs here in western Massachusetts.

• Down syndrome occurs when the cells contain an extra chromosome. The extra chromosome causes delays in development, mild to moderate mental retardation, and specific physical characteristics. Approximately one in 800 newborns is diagnosed with Down syndrome.

• Fragile X syndrome is a hereditary deformity of a specific gene (called
FMR1) on the X chromosome. This usually results in mild mental retardation, language delays, behavioral problems, and/or autistic-like behavior. It occurs once in approximately every 5,000 newborns.

• Rett syndrome, a disorder on the autism spectrum, includes mental retardation, loss of motor ability, and/or purposeless wringing of hands.
Recently, a specific gene – MECP2 – located on the X chromosome, was identified in children with this syndrome. Rett occurs in fewer than one in 10,000 births.

Identifying specific chromosome or gene abnormalities is a first step in learning more about these disabilities. Unfortunately, we still know very little about what causes these genetic disturbances. Some are passed down from parent to child, others might be random occurrences, and still others may be due to environmental factors.

What Causes Autism?
The cause of autism may turn out to be a combination of genetic and environmental factors. Currently, no specific genes or environmental factors have been identified. There continues to be a lot of speculation in the public about things that could cause autism, such as pollutants, viruses, and vaccines. Research findings, however, remain unconvincing and controversial.

Knowledge of the causes of developmental disabilities may help prevent future occurrences, but there are thousands of children and adults who need education and therapy today. We know that individuals with these disabilities can learn, grow, and lead high-quality lives. How can we support them? First, each person’s needs should be assessed to determine goals. Then, best practices (those with evidence showing their effectiveness) should be used. These include teaching in small steps, providing rewards, and guiding correct performance. Second, related medical conditions should be monitored and the potential positive role of medications should be considered. Third, support groups for individuals as well as families are available and are useful. Finally, many families may find genetic counseling to be valuable.

May Institute operates schools for children and adolescents with autism and other developmental disabilities in Arlington, Braintree, Chatham, and West Springfield, Mass., and in Freeport, Maine. We also provide residential and day services for adults. For more information, contact us at 800-778-7601, or at www.mayinstitute.org.

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