Grand Canyon University: BIO 457
February 15th 2015
The human genome is a very complicated and complex system. Because it is so complicated it makes the system very susceptible to damages and changes. These changes can come from the external environment such as being exposed to toxic chemicals or intrinsic factors such as inheritance of genes (Sehgal & Singh, 2014). In normal cases there are proteins in the body that can repair this damage, so the nucleotide will find the damage cut it out and insert a new strip of DNA. This system is called nucleotide excision repair and it is one of many systems that helps repair genes in the body. When it comes to Xeroderma Pigmentosum (XP) this is not the case, the nucleotide excision repair is not working in this disease, causing this persons DNA to stay damaged and has a phenotype with an OMIM number of 278700 (McKusik, 1986) . This disease is not only brutal to ones DNA but because their body cannot repair the DNA when exposed to UV light for even a minute it can have drastic affects. This disease was really described by two dermatologists from Vienna. They described the disease as xeroderma, which means parchment skin and then later added on the word pigmetnosum meaning that the person has parchment skin with pigmented abnormalities (Kniffen, 1986).
Nucleotide Excision Repair (NER)
XP is caused because of a faulty NER system in the DNA. This system is so important and so essential because it is so versatile. It does not just repair lesions in from UV induced pyrimidine dimers, but also can repair intra strand crosslinks and even chemical adducts (Nouspikel, 2008). The reason this is possible is because the NER does not try to find where the problem in the DNA is, but senses that there is a distortion and will go and fix it. So depending on the degree of the lesion in the DNA, and in the case of XP, a small lesion from UV-induced cyclobutane pyrimidine dimers, the...