Introduction
The downs syndrome is a genetic disorder which is commonly referred to as trisomy 21. The condition is caused by chromosomal translocation. Observed symptoms in individuals with this disorder include intellectual disability, weak muscle tissue and a characteristic facial appearance. It is characterized with a slow mental development. This condition is closely linked to other conditions, for example, affected individuals may have heart defects at birth, and they may also suffer the dysfunction of the thyroid glad, cases of sickle cell anemia, a type of blood cancer may also be reported in children with the disorder.
Behavioral development in children with this condition is inhibited; they develop behaviors at a late age as compared to children without the condition; they also learn language very slowly. It is difficult to understand their speech; People who have this condition suffer from memory loss (Alzheimer’s disease), a condition associated with old age at an early age.
Genetic abnormalities that cause this condition
Most cases of the downs syndrome occur from trisomy 21, this refers to an additional chromosome 21 in every body cell. Normally, all blood cells should have two chromosomes 21; however, individuals with the disorder have three. Translocation downs syndrome occurs during spermatogenesis or oogenesis whereby a part of chromosome 21 becomes attached to another chromosome during gametogenesis. Individuals with translocation downs syndrome have the usual two chromosome 21 copies in each body cell but also materials from chromosome 21 in all their body cells. Mosaic downs syndrome occurs when there is additional chromosome 21 in each body cell. This condition is normally not inherited; it occurs instantaneously during formation of gametes, or reproductive cells randomly, children can therefore acquire the condition from parents who do not have the disorder.
Genotypes and phenotypes related to this condition
Genotype refers to the genetic make up of an individual; phenotype refers to the physical characteristics of individuals usually influenced by the genotype and environmental factors. The genetic make up is composed of similar strands of gene alleles in each body cell; cells involved in the generation of the downs syndrome are the reproductive cells or the gametes, the malformation is mostly associated with spermatogenesis whereby a whole chromosome 21 is translocated during the formation of the sperm cell or some material in it is translocated during cell formation.
The fetus results from the fusion of the male gamete, the sperm, with the female gamete, the ova. The resultant fetus will therefore have an extra chromosome 21 in each cell of its body or some material from chromosome 21 will be present in every cell. The normal genotype is interrupted by the mutation of the chromosome 21; the usual number of chromosomes per cell is two.
When the genotype is interrupted during formation, the phenotype is also affected; the characteristics of individuals with this disorder are both behavioral and physical. The behavioral characteristics are as a result of cognitive development inhibition in people with the condition. The process of their mental development is retarded in children, their intellectual ability is very low and they learn language at a slower rate as compared to children without the condition, the physical characteristics are presented in the facial appearance of people with the disorder, they usually have a longer than normal face.
How the environment may influence
Development is a factor of genes and the environment. The behavior of a child is highly related to the environment he or she is brought up in. For example a child who grows up in an environment vested with thugs is bound to have some traits of thugs in his/her behavior if no immediate intervention is put in place in his/her development. The environment can also influence behavior in downs syndrome individuals. For example his/her intellectual capacity can be improved if the individual is brought up in a highly intellectual community.
Cognitive development is highly influenced by the environment and as such mental development in individuals with the disorder can be facilitated if they grow up in an intellectual surrounding. The environment can also influence their language learning process. If such individuals interact with other normal kids at the early stages of development, they can learn language faster as compared to when they are raised in isolation; they can learn words faster from their fellow kids.
Teratogens are environmental effects that occur during a sensitive stage of prenatal care that may affect the child to be born. Genetic disorders are as a result of gene mutations which occur internally and therefore these conditions are less influenced by the environment. Teratogens do not therefore play a role towards the acquisition of the downs syndrome to the born child. However pregnant mothers should attend regular clinical check ups from which they know the condition of their expected babies. They will be able to prepare better for the downs syndrome if they know in advance that their babies have the condition.
