Mutations Essay Example | Topics and Well Written Essays - 750 words

Mutations - Essay Example These events culminate in the creation of loops possessing extra-helical bases that can produce frame-shift mutations unless they are reversed by mismatch repair (Errol et al 54). In HNPCC, also known as Lynch syndrome, an inherited mutation located in the mismatch repair gene leads to MI replication errors going unfixed. In most cases, this results in length changes for di-nucleotide repeats for the nucleo-bases adenine and cytosine. Changes in the nucleotide repeats indicate a DNA repair system in fault that can lead, to growth of colon cancer cells. MI insertions and deletions cause inappropriate DNA repair, which leads to uncontrolled division of cells and growth of tumours. This paper provides examples of human diseases that result from mutations and the way these mutations give rise to the diseases. Mutations affecting transition in CpG islands is a common cause of colorectal cancer. O6-methyl-guanine DNA methyl-transferase, or MGMT, is a vital enzyme during the repair of DNA. The enzyme removes all cytotoxic and mutagenic adducts from O6-guanine found in DNA. This site is the most preferred attack point for numerous alkylating chemotherapeutic agents and carcinogens. The loss of MGMT activity can be triggered by hyper-methylating the CpG Island that is located in MGMT’s promoter region, and is culpable in most cases of colorectal cancer (Errol et al 71). ... In addition, hyper-methylation of MGMT can be used in pharmaco-epigenomics with methylated tumors showing more sensitivity to alkylating drugs utilized in chemotherapy (Errol et al 71). Another form of mutation can occur during alternative splicing, which causes Oculopharyngial muscular dystrophy, or OPMD. This disease is an autosomal dominant disease of the muscles, which occurs worldwide. Recent research has found that the disease’s genetic basis is in mutations to the poly-A binding protein gene, which involves short GCQ tri-nucleotide repeat expansions that encode the poly-alanine tract (Schwarz 76). The underlying mechanism, which causes triplet expansion of mutation of the gene, is yet to be elucidated, but the model of DNA slippage is thought to be a plausible explanation. Mutated alleles found in patients suffering from OPMD are most likely caused by (GCG)(2)(GCA)(3) and (GCG)(3)GCA and not because of GCG repeat expansions (Schwarz 78). Unequal crossing-over of the two PABP2 alleles, therefore, rather than slippage of DNA, is the best explanation for mutations that lead to OPMD. Practically, all mutations that patients with OPMD report are explained by unequal crossover. Mutations occurring during alternative splicing can cause breast cancer. Breast cancer cells, as do most other cancer cells, adapt to their environment via the generation of new genetic products by alternative splicing (Jeanteur 80). Analysis of transcriptome has shown that over fifty percent of the human genome encodes protein iso-forms by alternative splicing of pre- mRNA. Therefore, alternative splicing is utilized as a vital mechanism for the generation of the human proteome diversity. Additionally, the isoform-selective expression of genes is important in cellular