Katie+Buyse+Survival+of+Sickest

​ Survival of The Sickest Dr. Sharon Moalem

Excerpt One:

“First of all, there is no real agreement to what //race// means. On a genetic level, it’s pretty clear that skin color isn’t reliable. We’ve already discussed how the skin color of a transplanted population would change to match the level of ultraviolet exposure in its new environment. Recent genetic studies bear this out—in terms of common genetics, some dark-skinned North Africans are probably closer to light-skinned Southern Europeans than they are to other Africans with whom they share their skin color,” (page 61, //Survival of the Sickest//)

This relates to what we talked about in class one day when the article on genetic variations in Africa was passed out and discussed. The name of this article is “Africa offers genetic bounty,” and it tackles a different part of the same phenomenon that Dr. Moalem spoke of in his book. In the text, it was mentioned that North Africans bear many genetic similarities with Southern (Mediterranean) Europeans. However, in the article it referenced the fact that, “any two Bushmen in their stuffy who spoke different languages were more genetically different than a European compared with an Asian,” (1). In other words, this means that not only to Bushmen have a lot of genetic diversity, they are also much more different from one another than Asians are from Europeans. However, this may simply be explained by the fact that much of the borders in between Europe and Asia are political rather than geographical—Russia and Turkey are parts of both continents, and thus people that share similar culture, religion and appearance could be technically considered different “races.” Also, travel in the Western world is much easier, especially nowadays, than it is in Africa. Much of Africa remains undeveloped and with poor infrastructure that prohibits quick travel of people and ideas. Also, Africa is a land of many different climates, from arid deserts to wide grasslands to humid rainforests to beautiful beaches. These different “habitats” probably affected the evolution of the African genome at a faster rate than the European genome. Not to say that Europe doesn’t have varying climates, or that Asia is all the same, but the traveling between different parts can be done very quickly and affordably perhaps affecting the genome in these parts.

The realization that phenotypically diverse groups share so much more of the genotype than ever imagined will truly open up many doors in genetic technology and genetic engineering. Obviously, the more that is known about DNA, genes, gene expression and racial differences, the better scientists will be able to tailor medicines and gene therapy to fit patients. The article suggests that these ground-shaking genetic similarities will bring new breakthroughs into determining which genes cause which diseases, and which genes indicate how a certain person will respond to different treatments. According to the article, this technology “could have payoffs both within Africa and elsewhere,” (1). Hopefully within the next few years, more can be learned about this unexpected genetic similarities and dissimilarities that can change the way science and technology interacts with society.

I have always thought that genetics are very interesting and the surprising new breakthr0ughs (that Africans are very dissimilar genetically from one another) will hopefully be used to further our knowledge of genetics, and thus be used to further medicine. Since modern human life began in Africa, it makes sense to return to that source to further probe the genetic bounty that it offers. The book //Survival of the Sickest// is very interesting because it shows how things that are potentially harmful or not advantageous nowadays may have been very advantageous or beneficial in the past. Although this book was written for the average person, it does contain some very specific examples of particular genes or diseases that make it more interesting.

KB

EXERPT 2:

"Stems cells are 'undifferentiated' cells--in other words, they can divide into many different types of cells....Stem cells can produce many types of cells--the mother of all stems cells, of course, is the single cell that started you off in your mother...Stems cells are not subject to teh Hayflick limit--they're also immortal. They pull of this feat by using telomerase to fix their telomeres the same way that some cancer cells do. You can see why scientists believe stem cells have such potential to cure disease and alleviate suffering--they have the potential to become anything, and they never run out of steam," (188-189).

In our class, we spent a great deal of time discussing stem cells, culminating with Dr. Lichtler’s guest lecture. We discussed many parts of stem cells, such as the germ layers they formed, what they can turn into, the differences between adult stem cells and embryonic cells, the differences between totipotent and pluripotent and all sorts of things along those lines. In this excerpt, Dr. Moalem mentions stem cells and their effect on medicine. Stem cells don’t follow Hayflick limits—that means that there is only a certain amount of times that a cell can divide. After it divides a certain number of times, it can no longer do that anymore. This is a check against cancer. However, cancer cells and stem cells have the enzyme telomerase in their arsenals. For stem cells, this provides unlimited divisions for much needed cells. In cancer cells, on the other hand, this enzyme allows it to divide limitlessly, causing the growth of tumors. This image helps to show the importance of telomeres in human cells.

This relates to course themes through science, technology and society. Stem cells are, perhaps, one of the most promising avenues of science today. These cells have the potential to cure injuries and diseases that we once thought could never be fixed. This will have great ramifications upon our society. The Henrietta Lacks controversy shows science at its most troubling—cells being used for a profit without the permission of Henrietta or her family. Although stem cells have shown great potential for furthering the aims of science, they also have the potential to further blur ethical lines. Ihope that in the next couple of years, stem cell therapy becomes more common and more effective. The potential stem cells have are amazing, and hopefully we will be able to enjoy them soon.

Works Cited

(1) Moalem, Sharon, and Jonathan Prince. // Survival of the Sickest: the Surprising Connections between Disease and Longevity / Sharon Moalem with Jonathan Prince. // NY: HarperCollins, 2007. Print

(2) Telomeres. Digital image. Web. 2 June 2010. .

POST THREE

Excerpt: “If your macrophages lack iron, as they do in people who have hemochromatosis, those macrophages have an additional advantage—not only do they isolate the infectious agents and cordon them off from the rest of the body, they also starve those infectious agents to death,” (page 13).

In healthy people, macrophages have continual access to iron, which is actually counterproductive, because some types of bacteria that are captured by macrophages can grow strong off of the iron and then stage another attack on the immune system. However, in people with hemochromatosis, all cells of the body are over stuffed with iron, with the exception of macrophages, which are “anemic” in the sense that they are starved for iron. But because they have no iron, they are able to isolate infectious agents without allowing those agents to beef up on iron, like the macrophages of a healthy person would. Because of this, people with hemochromatosis faced a genetic advantage during the Black Death and against all disease in general. However, the trade off is that people who unknowingly suffer from hemochromatosis face organ failure as the levels of iron reach dangerous levels. This ties into our course curriculum very clearly as we spent a lot of time talking about evolution and it’s ties to the heterozygous advantage. “If individuals who are heterozygous at a particular gene locus have greater fitness than the homozygotes, natural selection will tend to maintain two or more alleles at that locus,” (1). This excerpt from our textbooks helps to explain the phenomenon that Dr. Moalem is trying to discuss. In populations that live in humid, swampy, tropical areas, many mosquitoes carry a protozoan that causes malaria. Malaria sickness is one of the most deadly diseases in the world, especially in areas with little medicine to combat it. However, nature has found a way to help fix this. The disease known as sickle-cell anemia causes a conformational change to hemoglobin. It is dangerous in the homozygous form, however, in people that inherit one “sickle” allele and one “healthy” allele, their hemoglobin is only slightly curved, a trait that allows them to escape the worst effects of malaria. This does not provide immunity from the sickness, but it does afford protection from becoming seriously sick. Analysis of gene frequency in parts of Africa has shown that the sickle cell allele has a frequency of 20%! (2). This is confirms the theory of heterozygous advantage. To apply this to //Survival of the Sickest//, the author notes that people who have hemochromatosis and those who suffer from anemia essientially starve their macrophages by locking out the iron. And rather than killing them faster, this iron lockout is actually what is helping them fight off diseases such as the bubonic plague, tuberculosis, brucellosis and meningitis (2), just like carrying one copy of the sickle allele affords some protection from the deadly malaria.

This is very interesting to me because it initially seems counterproductive to have a body that cannot recognize when enough iron is present. And, indeed, it is very dangerous, yet it does offer some protection from the nastier infections and diseases that could be picked up along the way. I also think it is fascinating that hemochromatosis is the most common genetic disorder in people of Western European origin only because of the almost-supernatural protection it has provided to people throughout many deadly outbreaks of disease.

Works Cited

1. Textbook

2. Moalem, Sharon and Price, Jonathan. //Survival of the Sickest.// 2007

POST FOUR:


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