SMA (spinal muscular atrophy) is a disease that robs people of physical strength by affecting the motor nerve cells in the spinal cord, preventing their ability to walk, eat or breathe. It is the leading genetic cause of death among newborns. SMA is caused by a mutation in the survival motor neuron 1 (SMN1) gene. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Spinal muscular atrophy (SMA) types o, 1,2,3, and 4 are inherited as abnormal recessive genetic disorders are associated with abnormalities (mutations) in the SMN1 and SMN2 genes on chromosome 5 at the chromosomal locus 5q11 -q13. SMA1 is believed to be the primary disease caused by the genes. Approximately 95-98% of affected individuals have deletions in the SMA 1 gene, and 2-5% have specific mutations in the SMA 1 genes that result in reduced production of SMN proteins. When three or more copies of the SMA 2 gene are also present, the disease may be milder. Genetic diseases are determined by the combination of genes for a particular trait that are found on the chromosome received from the father and mother. Recessive genetic disorders have occurred when an individual inherits the same abnormal gene or trait from each parent. If an individual has received a normal gene and a gene for the disease, the person will be a carrier of the disease, but will usually show no symptoms. The risk that two carrier parents will both pass on the defective gene and, therefore, have an affected child is 25% for each pregnancy. The risk of having a child who is a carrier like the parents is 50% for each pregnancy. The chance that a child will receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females. Biological markers or surrogates for developing smears. Please note: this is just a sample. Get a custom paper from our expert writers now. Get a Custom Assay These potential surrogate markers studied to date include: Measurement of the quantity and ratio of full-length and truncated SMN2 RNA transcripts, as well as SMN proteins from white blood cells or fibroblast culture. Count of motor units that showed correlation with the number, age and functions of 2 SMN copies. Quantitative ultrasound in the evaluation of muscle changes in patients with SMA. Electrical impedance. A longitudinal study of surrogate markers will be necessary before any of them can be used in an intervention study.