Down's syndrome, which is detected in approximately one in 1000 people every year, occurs when a person inherits three copies of chromosome 21 rather than the normal compliment of two, and this presence of an extra set of genes leads to over-expression and increased production of certain products that cause the abnormalities observed in the syndrome (Murphy pp).
Every child with Down's syndrome will possess some level of learning disorder, ranging from severe to very mild mental retardation, however the majority will learn to walk, talk, read and write (Murphy pp). Roughly 40% of infants born with Down's will have some sort of heart defect, such as a hole in the heart (Murphy pp). There can also be problems regulating their temperature, which can cause very dry skin, and moreover, weak an immune system is common in these infants, making them prone to infections, especially chest and sinus infections (Murphy pp). Down's children generally have chubby faces with protruding eyes and tongues, eyes that slant outward and upward, ears that are smaller than normal, and the back of their head is flat (Murphy pp).
In 1866, John Langdon Down published an essay describing a group of children with common features who were distinct from other children with mental retardation (Murphy pp). He referred to these children as Mongoloids because of his belief that they looked similar to people from Mongolia, who at the time were mistakenly thought to have an arrested development (Murphy pp). Down believed the condition to be a result of tuberculosis in the parents, and the name Mongoloid continued to be used until the 1960's when it became known as Down's Syndrome (Murphy pp).
During the 1930's, researchers first began to speculate that Down's syndrome was caused by chromosomal abnormalities, and in 1959, researchers Jerome Lejeune and Patricia Jacobs discovered the cause to be triplication of chromosome 21 (Murphy pp). Down's syndrome, also called trisomy 21, occurs when there is an extra copy of chromosome 21, the smallest of the 23 human chromosomes, and this extra set of genes results to the over-expression of the involved genes, causing increased production of certain protein products (Murphy pp). For most genes, over-expression has little effect, however the genes that cause Down's syndrome are exceptions, and it is believed that only a small number of genes spread over the chromosome are involved in causing the syndrome (Murphy pp).
There is a wide variety of features and characteristics of people with trisomy 21 (Murphy pp). The first possible cause is that genes are triplicated, but also genes come in different forms called alleles, and the effect of over-expression of genes can depend on which allele is present (Murphy pp). Pentrance also plays a part, which means that the same allele that causes a condition in one person may have no effect on another person (Murphy pp). Moreover, there are other forms of Down's in a small percentage of cases, in which other chromosomal variations are to blame (Murphy pp).
In the June 22, 2002 issue of Journal of Special Education, Elizabeth M. Dykens states that Down syndrome is the most common genetic, chromosomal, cause of mental retardation, and that in nearly all cases is caused by a third Chromosome 2 (Dykens pp). Aside from particular genetic and physical features, the majority of children with Down syndrome display specific problems in linguistic grammar, expressive language, and articulation (Dykens pp). For example, "most children with Down syndrome do not progress grammatically beyond the 3-year level, and their grammatical abilities almost invariably fall below their overall mental age levels" (Dykens pp). Moreover, skills in expressive language, as opposed to those in receptive language, are more significantly delayed (Dykens pp). In fact, by the time children's mental ages reach twenty-four months, remarkable delays, six or more months, in expressive language abilities are evident in 83% to 100% of children with Down syndrome (Dykens pp). And regarding articulation, 95% of parents of Down syndrome children report that others show at least occasional difficulties understanding the speech of their child (Dykens pp).
Dykens reports that other areas are relatively strong in most children with Down syndrome (Dykens pp). For example, researchers have found that on average, school-age children with Down syndrome demonstrate levels of visuo-spatial short-term memory that are one or more years advanced over identical auditory or verbal short-term memory tasks (Dykens pp). Dykens notes, such "relative strengths arise even when subtests from different psychometric instruments are used to measure verbal short-term memory and when researchers use either scaled or age-equivalent scores in their analyses" (Dykens pp). Thus, as a group, children with Down syndrome show significant, more than mental-age level, deficits in grammar, expressive language, and articulation, yet also demonstrate relative strengths in visual short-term memory tasks (Dykens pp).
Although no cure or prevention has been found as yet, research indicates that the limitations associated with Down syndrome are not as uniformly extensive as once thought (Appl pp). In the September 22, 1998 issue of Childhood Education, Dolores Appl states that while the exact upper developmental limits or the changes over the life span are not fully understood, it is known that intervention can help children with Down syndrome in reaching their potential (Appl pp). Down syndrome is a fairly common and well-known syndrome, however misconceptions often lead to stereotyping, which can be disconcerting to parents, and detrimental to the children due to the potential for low expectations in the learning environment in relation to low performance (Appl pp).
Children born with Down syndrome are more likely than "typically developing children," to possess particular characteristics, yet not all children will be affected similarly, nor will the degree of involvement be the same (Appl pp).
Moreover, certain characteristics, such as those related to language development, may become more obvious with age (Appl pp). Appl notes that characteristics found in individuals with Down syndrome may also be found in individuals with other syndromes, and as of now, it is not known whether any characteristics are unique to Down syndrome (Appl pp). Thus, it is important that educators not uniformly apply characteristics to all children with Down syndrome, but rather, "the characteristics should be used as a means for understanding and supporting individual children with Down syndrome within the specific contexts of their physical and social environments" (Appl pp). Appl cautions that it must be remembered that considerable variation exists in the physical development, medical conditions, mental abilities, and behavior of individuals with Down syndrome (Appl pp).
Common physical characteristics of children with Down syndrome included the distinctive appearance of their facial feature, head shape, feet, and hands, yet these features do not interfere with their development and learning, nor is there any connection between the number of distinctive features and mental ability (Appl pp). However, according to Appl, hypotonia, or low muscle, which is present in the majority of infants with Down syndrome, is likely to affect learning and development (Appl pp). Appl notes that hypotonia tends to be present to some extent in all muscles of those afflicted, causing the muscles to feel flaccid and floppy, however the degree of low tone varies among different children with Down's and in different parts of the body within the same individual (Appl pp). Yet, hypotonia diminishes with age and early intervention can play a major role in minimizing its negative effects (Appl pp). Hypotonia affects the strength and movement of Down's children and if often accompanied by excessive joint flexibility, which reduces stability in the limbs (Appl pp). Thus, many children with Down syndrome experience delays in the development of major motor skills, which in turn can hinder their ability to explore and gain mastery over their environment (Appl pp). Moreover, notes Appl, hypotonia can negatively affect other areas of development, including language and feeding skills (Appl pp). Children with Down syndrome also have a higher incidence of medical problems such as "cardiac defects, respiratory and intestinal problems, vision and hearing difficulties, hypothyroidism, vertebrae instability, umbilical hernia, and obesity" (Appl pp).
In the 1999 Dementia, Aging and Intellectual Disabilities: A Handbook, Brian Chicoine and co-authors state that the occurrence of Alzheimer's disease among individuals with Down syndrome is a great concern for families and care providers of adults with Down syndrome (Chicoine pp). Previous research has found that all adults with Down syndrome over the age of 40 develop plaques and tangles in the their brains that are similar to those found in Alzheimer's patients, thus most parents and professionals alike conclude that all adults with Down syndrome will develop Alzheimer's disease (Chicoine pp). However, Chicoine cautions that this conclusion is mainly based on autopsy data without similar evaluations of pre-morbid clinical data (Chicoine pp).
Chicoine suggests that in addition to annual evaluation by professionals, such as physicians, social workers, nutritionists, and audiologists, it is important that thyroid blood tests are ordered annually as well (Chicoine pp). Chicoine notes that hypothyroidism, atlanto-axial instability, chronic hepatitis and other health problems are common in people with Down syndrome…