Genetic Disorders

Genes are the basic hereditary units which consist of DNA sequences that encode information for the synthesis of specific proteins. These genes also determine the phenotypic expression as well as the personality expression and behavioral patterns. The abnormalities in an individual’s genome are known as genetic disorders which are either inherited or caused by mutation in the pre-existing genes (Shiel, 2010). Genetic disorders can be categorized into four classes which are single-gene disorder, multi-factorial inheritance, chromosomal inheritance and mitochondrial mutations. (Refer to Figure 1, Appendix 1). Each disorder is further discussed based on their characteristics and diseases symptoms.

The first type of genetic disorder is the single-gene

Russell (2010) claims that the change in the chromosomal number and structure form of wild type condition is known as chromosomal mutation (p. 464). The wild type chromosomal complement consists of 46, XY for males and 46, XX for females. Chromosomal mutation occurs during the meiosis and mitosis, where the chromosomes complement is not an exact copies of 23 pairs at the end of the cell division. Two different type of zygote: trisomic (2n+1) and monosomic (2n-1) respectively produce when such gametes fuse with the wild type (Kumar et al., 2005). Whereas the structural changes in chromosome which causes by deletions, duplications, inversions and translocation are known as chromosomal structure mutation (Russell,

Vary from Mendelian disorder which is cause by mutations in nuclear DNA, mutation in the non-chromosomal DNA of mitochondria is mainspring of mitochondrial disorder (Shiel, 2010). Smith et al. (2007) state that only 25% of the affected kids show the symptoms of the syndrome and 90% will be express during puberty. Mitochondrial genome is plentiful in the cytoplasm and intensely tiny while the nuclear genome is big in size which found in the nucleus of a cell. Since mitochondrial DNA are plenty within the cytoplasm of the ova it is transferred to their generations which known as maternal inheritance (Kumar et al., 2005). Leber's hereditary optic atrophy and is kind of mitochondrial disorders. The mutations in the mitochondrial DNA and transferred in a maternal pattern leads to optic nerve dysfunction (Dufier, 2003). Patients may endure an unexpected on-set sightlessness in their mid-age because of the death of optic nerve (Wallace,