Proto-Oncogenes Their Role in Cancer Article Example | Topics and Well Written Essays - 1250 words

Proto-Oncogenes Their Role in Cancer - Article Example Specific genes of chicken and rodent retroviruses were first noted to transform normal mammalian cells in culture. These cancer-causing genes (oncogenes) proved to be activated homologues of mammalian genes (proto-oncogenes), which were stolen from the host cell during viral evolution. Primary human cancers harbor similarly activated alleles of proto-oncogenes (Haber, 2006) Some of the mechanisms by which proto-oncogenes are activated in human cancers include: point mutations, gene amplification, and chromosomal translocations. These mutations are known as gain-of-function mutations because â€Å"they result in novel or altered functional properties for the encoded protein and are genetically dominant over the second normal allele†(Haber, 2006) Proto-oncogenes can be classified based either on their normal function within cells or upon sequence homology to other known proteins (National Science Teachers Association. 2001). â€Å"Proto-oncogenes that were originally identified as resident in transforming retroviruses are designated as c- indicative of the cellular origin as opposed to v- to signify original identification in retroviruses† (National Science Teachers Association. 2001). The classification listed below includes only those genes that have been highly characterized (National Science Teachers Association. 2001). Of particular interest is the ras family of proto-oncogenes. There are three homologs of this gene, H-ras, K-ras, and N-ras, and these have been detected in more human tumor types and at a higher frequency than any other oncogene (Anderson et al., 1992). They acquire transforming activity by a point mutation in their coding sequence. Invivo, activating point mutations have been observed in codons 12, 13, 61, 117, and 146 (Anderson et al., 1992).