In an article published recently, researchers discussed a new finding that a blood sample taken from the mother can show fetal DNA. If perfected, this technique could lead to widespread non-invasive genome sequencing. Currently, invasive procedures such as amniocentesis are used to collect fetal DNA. There are risks with these procedures which is why there is so much excitement surrounding this non-invasive technique. Back in 1997 one researcher discovered the presence of “floating” fetal DNA in the blood of the mother. While much more work needs to be done to perfect, improve, and reduce the cost of this new procedure, the process involves taking a blood sample from the mother and working to isolate what little fetal DNA may be in the blood sample. In this particular study, a blood sample was taken and researchers sequenced 4 billion DNA molecules, the genetic maps of the father and mother were compared, looking for places where the maternal and paternal genetic inheritance differed in the fetus. Distinguishing the fetal DNA is challenging since it is surrounded by “an ocean of DNA that had been released by the maternal cells”. Once the genome map has been established for the fetus, it can be scanned for variations and mutations. While still in the earliest stages of research, this finding seems promising in regards to eliminating risky invasive procedures to identify genetic diseases in unborn children
A British Columbia biotech company, Okanagan Specialty Foods, boasts their ability to genetically modify an apple to not turn brown after it is sliced. The modification takes place by silencing the genes responsible for the enzyme polyphenol oxidase, which is responsible for the quick browning of sliced products. This process has been tested for five years and has succeeded in raising non-browning Galas, Fujis, Goldens and Grannys. Relevant to our current class discussion on the ethics of genetics, some organizations are concerned with the safety of genetically modified crops and current food regulations on the labeling of these products for consumer knowledge. Other concerns regard the deception of consumers, as products may appear fresh when in reality they have been modified to not decay. The company is still waiting for a permit to be able to market and distribute these apples in the U.S. And the political debate continues….
A recent study has shown that a duplicated region of DNA on chromosome 5 predisposes people to depression. This gene is involved in the development of nerve cells, which furthers previous research that disruptions in neurotransmission networks are the basis of depression disorders. Of the copy number variations (CNV) identified in the study, 12 were exclusive to patients with major depressive disorder. A duplication of DNA on chromosome 5 was identified in 5 unrelated cases and was not observed in unaffected controls. This area of chromosome 5 is also the location of the gene SLIT3 which is important for axon development, consistent with the previous understanding that these disorders stem from disruptions in the neuro networks. Future studies with advanced sequencing technology are expected to reveal more CNVs and mutations of the gene SLIT3. In the future these studies may provide the basis for more specific drugs to combat major depressive disorders.
“The next big wave” of cancer research seems to be exploiting the unique metabolism of cancer cells, according to Dr. David Schenkein, chief executive of Agios Pharmaceuticals. In this article from the New York Times, researchers discuss the possibilities of fighting cancer by depriving the cells of nutrients. Their “voracious appetite” for glucose fuels the rapid growth of cancerous cells. While previous research focused on finding target drugs to the genetic accelerators of tumors (the signals for tumor growth), these drugs were often ineffective as many tumors had more that one type of accelerator to target. The idea behind this new line of research suggests that depriving the tumors of their beloved glucose should “render the accelerators ineffective”. While it might seem simple to starve cancer cells by lowering blood glucose levels, in fact it is more complicated than this. Our bodies are highly efficient at regulating blood glucose levels, even when we are starving, AND, even if there were low levels of glucose, cancer cells which are highly adept at extracting glucose, would be the last surviving cells. For these reasons, research is focusing not on lowering glucose levels, but instead on exploiting the unique ways in which tumor cells utilize glucose. Unlike normal cells, cancer cells turn glucose into energy by glycolysis, even in the presence of oxygen. Drugs are being developed that exploit this difference in tumor cell metabolism or that target enzymes unique to tumor metabolism. Another important difference between normal cells and cancer cells is that cancer cells do not commit suicide. One theory is that cancer cells do not commit suicide because they lack sufficient energy. Chemical inhibitors are being studied that alter the metabolism of cancer cells, moving them away from glycolysis and making them more efficient at producing ATP. These drugs have been studied in genetically engineered rats and have shown to be effective in slowing the growth of lung tumors.
Scientists claim to have cited the fastest case of human evolution. A study between the genomes of Tibetan and Han Chinese peoples have led scientists to identify a difference in genes that allows Tibetans to live at very high altitudes without experiencing altitude sickness. The study identified at least 30 genes that had undergone evolutionary change in the genomes of Tibetans. The biologists at the Beijing Genomics Institute cite that the split between the Han Chinese and the Tibetans happened only 3,000 years ago, meaning that this would be the most recent case of evolutionary change. However, archaeologists argue that the split happened no less than 7,000 years ago, which would put this case on the playing field with the evolution of genes for lactose tolerance in adults.
The study was completed by a group of biologists who analyzed the genes of 50 Tibetans who live at altitudes of 14,000 ft above sea level and 40 Han Chinese who live 160 ft above sea level. About 30 genes were found to be rare among the Han but common to the Tibetans. This difference indicates that the gene common to the Tibetan people is due to natural selection. The favored version of the gene, HIF2a, found in Tibetans, allows for fewer red blood cells which prevents the blood from thickening as the body tries to counteract the low oxygen levels by producing more red blood cells. This variation of the gene indicates how Tibetans can live at such high altitudes without suffering altitude sickness.
On an interesting side note, a major social concern regarding the implications of this genetic difference between Tibetan and Han Chinese stems from a long struggle for Tibetan people to achieve political autonomy. Researchers hope that this study doesn’t impede Tibet from accomplishing this autonomy “given that it is cultural history and language, not genetics, that constitute a people”, as stated by Dr. Nielson.
