On pages 172 - 173 of Survival of the Sickest, Dr. Moalem mentions the Indian practice of chewing betel nuts to give an example of the potentially deadly effects of methylation/hypermethylation of certain genes by consumption of methyl markers through smoking, eating, etc... This information on methylation/hypermethylation is related to Big Idea 4 (Biological systems interact, and these interactions possess complex properties) in that the methyl markers attached to the DNA genes through methylation inhibit normal protein production and protective functions such as self-destruction of lone cancer cells, as stated by Dr. Moalem.
Define methylation and explain the process of methylation (consumption of methyl markers, methyl markers' attachment to DNA genes, how the methyl markers inhibit proper function of the genes in DNA repllication, transcription, translation, and protein synthesis) at the molecular level. Then, give an example of methylation and a specific methyl marker that causes a deadly effect such as cancer, incorporating the process of methylation of genes at the molecular level in the example. Also, state why methylation of genes is a selective disadvantage and a harmful effect on the body.
Paul Sone (jsone4@students.d125.org)
Methylation is a process by which the expression of a gene is altered without changing the gene itself. Methylation often occurs because of environmental stimuli or various lifestyle choices. In most cases, methylation is associated with turning off genes rather than turning on genes. Methylation of genes occurs when methyl groups, which are groups of one carbon and three hydrogens (CH3), land on top of a gene and change its expression. This relates with Bigh Idea 4 (Biological systems interact, and these systems and their interactions possess complex properties) in that methyl marker interact with the human genome. As a result, in many cases the methylated gene does not synthesize the protein, which the gene was originally instructed to make. At the molecular level, methylation prevents transcription factors from binding to the DNA base cytosine. Transcription factors along with mediator proteins, RNA polymerase II, and enhancers form the transcription initiation complex, which is correctly placed on the promoter and facilitates transcription (Campbell 360). Therefore, if transcription factors cannot bind properly, pre-mRNA cannot be transcribed. Needless to say, without pre-mRNA, there is no RNA for translating into amino acids and ultimately synthesizing proteins. (http://www.imgenex.com/tech_dna_meth.php)
ReplyDeleteAs previously mentioned, lifestyle choices such as “smoking” can cause methyl markers to “build up around cancer-fighting genes.” (Moalem 172). In Germany, scientists from Epigenomics discovered that methylation of the PITX2 gene is linked with high rates of breast cancer. Evidently, the PITX2 gene fights against breast cancer. Therefore when the PITX2 gene is highly methylated, the PITX2 gene cannot synthesize its proteins used for fighting breast cancer. (Moalem 172) Without these proteins, cancerous cells can reproduce rapidly and form tumors. For instance, in carcinomic breast cancers a cancer can begin at the epithelial cells of the breast and reproduce uncontrollably, eventually forming a malignant tumor. (http://www.cancer.org/cancer/breastcancer/detailedguide/breast-cancer-what-is-breast-cancer)
As this example of methylation illustrates, methylation can be a selective disadvantage. If our ancestors, for example, smoke habitually, then they will develop methyl markers that can attach to genes that fight cancer. The problem though is that these methyl markers can be inherited for generations. Therefore, the descendants are more predisposed to get cancer and will have a smaller chance of surviving and reproducing.
-Ken Saito (ksaito4@students.d125.org)