Rebecca+Lichtler+Survival+of+Sickest

Post 1
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Excerpt
“A healthy adult usually has between three and four grams of iron in his or her body. Most of this iron is in the blood stream within hemoglobin, distributing oxygen” (pg 7)

[[image:http://lomalindahealth.org/health-library/graphics/images/en/19443.jpg]] Response
This quote relates to the concept of the structure of a substance relating to its function in the body. Hemoglobin is a protein that is made up of four different chains, two alpha and two beta. Each alpha chain holds 141 amino acids and each beta chain holds 146 amino acids (Hemoglobin Structure and Function). When each chain is folded up, part forms the heme group. Each heme group has an iron at the middle. Where the structure of hemoglobin starts to become important is in the heme groups. Because there are four heme groups, each hemoglobin can hold four oxygen molecules. This is illustrated in the diagram, in which each blue circle is an oxygen molecule, and each one is attached to the separate heme group. Because hemoglobin is a protein, this excerpt also relates more generally to the study of macromolecules that we covered in the beginning of the course. Hemoglobin is an excellent example of the importance of the different levels of protein structure. The primary structure is important because that is what causes there to be two different types of chains, the two alpha and two beta (Tamarkin). The tight coiling of the secondary and tertiary structure allows the hemoglobin to tightly bind to oxygen and carry it throughout the blood stream. The quaternary structure of the hemoglobin is obviously important because it allows for each protein to carry the four oxygen molecules.

Something that was interesting about the focus of the author was that he did not mention much on the evolution of these specific advantages of hemoglobin. The presence and structure of hemoglobin had to have evolved to be as functional as it is now in "a healthy adult". The quote relates directly to the theme of evolution, in that hemoglobin, like all other advantageous features of any organism, had to have evolved to be what they are. I found this strange because the purpose of his book is to explain why different illnesses have evolved the way they did. One would think that if a person was trying to describe the evolution of a disease related to the iron content of hemoglobin they would at least comment on the evolution of the protein itself, and the qualities that make it important. It seems like it would be important for them to discuss evolution and genetic change on the more specific levels of the molecules and cells themselves, as well as the general idea of the evolution of disease as a whole. One aspect of the book that I don’t really understand so far is how the author can almost completely disregard the importance of hemoglobin, and therefore iron, in the carrying of oxygen throughout the body, which is possibly one of the most important processes. oxygen is needed to create ATP, which is needed in every singe process the body carries out. I understand his theory that if bacteria need iron, the less iron we have the less bacteria and therefore the less sickness. However, people do need iron to survive. This position is understandable, though, because it helps prove his point that illnesses like anemia and hemochromatosis were helpful in preventing the contraction of certain diseases throughout history. It does seem like he is misleading the public a little though, by implying that iron is not important, and that all it does is create a better environment for bacteria, which is not entirely true. However, again, this was not the purpose of the book, the purpose was to point out new ideas, not restate old ones.

Post 2
“As everybody knows, skin color changes, to some extent, in response to sun exposure. The trigger for that response is the pituitary gland. Under natural circumstances, almost as soon as you are exposed to the sun your pituitary gland produces hormones that act as boosters for your melanocytes, and your melanocytes start producing melanin on overdrive”(53-54) This quote relate to the subject of animal physiology, specifically the endocrine system. The endocrine system is made up of the various glands and the hormone they secrete. Besides the pituitary, other main glands of the endocrine system include the hypothalamus, the thyroid, and the adrenal glands. The pituitary gland is responsible for producing several hormones that regulate the female reproductive system, as well as antidiuretics and pain response hormones, along with the ones that boost the melanocytes(2). These are actually called MSH, or melanocytes-stimulating hormones(1). All hormones of the endocrine system have both a source and a target. The target can be one specific organ or more. For example, insulin target almost every cell in the body, while glucagon exclusively targets the liver, those both of these hormones regulate glucose content of the blood. The overall purpose of the endocrine system is regulation and maintenance of homeostasis. Most of the time they come in antagonistic pairs. Back to the example of insulin and glucagon, these two hormones secreted by the pancreas work together to balance out the glucose levels of the blood. After a large intake of carbohydrates, more insulin is triggered to be released to decrease the amount of sugar present. However if a long amount of time passes without replenishment of glucose, glucagon will be triggered to release more into the blood stream to provide more energy. This is in an attempt to ensure that there is always the proper amount of glucose in the blood stream. This same principle is d emonstrated in the example given by Moalem in the book. When the body is exposed to sunlight, MSH tries to regulate the amount of melanin active in the body by activating the melanocytes. The more melanin produced, the less harmful ultraviolet light the skin absorbs. This again is a less direct attempt at regulation, but instead of something as tangible as the amount of glucose present in the blood, it is regulating the amount of light “present” in the skin. In this part of the book I have noticed in improvement on the partiality of the topics that Moalem focuses on. In this section on the benefits and risks of the sun, he acknowledges that the sun both increases our vitamin D content, but that people with less melanin in their skin are certainly at risk for damage from the UV rays of the sun. What makes this section so different from the one on hemoglobin is the highlighting of the dangers of folic acid deficiencies because of exposure to the sun. for me it legitimizes some of his claims, by not saying that all of these discoveries he has made prove that everything we thought was bad is actually good. It makes his other claims seem more believable, because he is including both positive and negative discoveries.

Post 3
 Excerpt "By reconstructing the genetic history of one of the genes responsible forthe growth of bitter taste receptors in our tongues, scientists have traced the evolution of this ability to Africa, some 100,000 to 1,000,000 years ago. Not all humans have the ability to taste bitterness--and not all are as sensitive to it as others--but given how widespreasd the ability is across the globe, it's pretty clear that tasting bitterness gave humans a significant survivial advantage." This quotes relates directly to the exercise done in class, where we tested the classes ability to taste bitter, by first using a control paper, and then a paper with PTC. If a bitter taste was sensed from the PTC paper, that person was labeled a taster, if not they were a non-taster. These differences are the result of a genetic mutation. This mutation developed and remained because of the fact that in nature, bitter tasting plants, and substances in general, tend to be dangerous. The mutation has persisted because being able to sense bitterness gave these particular humans an evolutionary advantage, because they were less likely to consume and digest a poison, thus enabling them to reach reproductive age and pass the mutation onto their offspring. The way in which various genes are maintained is expressed in the equation of Hardy-Weinberg equilibrium. This equation has to do with allele frequencies in a population and reads p2 + 2pq + q2 = 1. In this, p represents the frequency if the dominant allele and q represents the frequency of the recessive allele. So, for this example p2 + 2pq would be the number of tasters, because the mutation for tasting bitterness is dominant. The number of non-tasters would be q2. This relates to inheritance and heritability as a whole as well. The fact that the gene for bitter tasting is dominant means a person must only possess that one dominant allele in order to taste bitterness. They only possible way for them not to be able to taste bitterness would be to inherit two non-tasting alleles. Even then, according to studies done on the subject, a non taster actually has only an eighty percent chance of not being able to taste bitterness(1). This quote relates to the biological concept of continuity and change. There are certain things in nature that one would think would have disappeared by now, or that humans could have made disappear. One of these is poison. However, when viewed under the lens of the theme continuity and change, it makes sense. This theme states that evolution involves both things staying the same, and things changing. The example of poisonous plants and the advent of the bitter gene is an example of this. In the figurative sense, humans could not afford to just wait and see if plants were going to evolve out of being poisonous so they could eat whatever they want, something about us had to change. In more technical terms, the continuity of the plants being poisonous let to a change, or mutation in the gene for sensing taste. This goes against the often-conceived concept that evolution is all about change. In fact, if the plants had evolved to be non-poisonous, the presence of the bitter tasting gene would not have become so widespread. So sometimes, something has to be remaining constant in order to incite an evolutionary advancement. 1. "Bitter Taste Perception - Genetic Testing - 23andMe." //Genetic Testing for Health, Disease & Ancestry; DNA Test - 23andMe//. Web. 08 June 2010. . Post 4 Excerpt "A new series of research is beginning to demonstrate that the previous assumption that so-called junk DNA is junk-was bunk." (128) This quote refers to the vast amount of DNA in the human genome that does not code for proteins. Only about 3 percent of DNA does, and for many years it was thought to have no purpose, or even be detrimental, which Moalem alludes to when calling it “parasitic.” In the paragraphs following this quote, Moalem describes the source of some of this DNA. He describes how bacteria and viruses actually have contributed their DNA to human DNA by existing as remnants of a symbiotic relationship that existed in our prehistoric non-human ancestors. He also mentions how this junk DNA is not actually junk, but just “non-coding”. He does not however mention what purpose it has, if it does not code for proteins, but isn’t junk either. In class we received an article about junk DNA that suggested that junk DNA plays a role in making each of us different, even if we have very similar coding DNA. Junk DNA may be a contributing factor of why some genes are expressed, and why some aren’t. It may explain why, along with environmental reasons, if there are two people with the same genetic risk for cancer and the same lifestyle one may get cancer three times in their life, and one may live until 92 and die by getting hit by a bus. This relates to the theme of regulation, because the non-coding DNA regulates which genes are expressed at what times. The article we read talked about how small changes in non coding DNA are more likely to be the cause of changes of the expression of traits as opposed to mutations in genes which are “ much more likely to have catastrophic effects than variations in non-coding DNA” (1). The article also focuses on the potential impact that knowing about non-coding DNA will have on the treatment of different diseases, some diseases that were not typically thought of as being specifically genetically related, just because scientists could not find a gene related to them in coding DNA. It mentions how the non-coding DNA can influence how transcription factors can behave differently in different people. Transcription factors are what initiate the process by which information from DNA is transferred to RNA, which will be eventually transferred to tRNA, which makes proteins. Of course, this all occurs from coding DNA, that’s why its called coding DNA. However, this process only happens if transcription factors activate it. But what activates the transcription factors? Many scientists believe the answer to this question is in the nucleotide sequences in non-coding DNA. Now having read farther in to the book I’ve noticed something’s that aren’t really inaccuracies, just little things that don’t seem to be exactly correct. For example, Moalem refers to non-coding DNA as being parasitic, and then goes on to explain this as meaning that it was ”not hurting us, not helping us, just helping itself” (128). Now he probably just meant parasitic in a les specifically biological definition, but considering this is a biology themed book, he could have just taken the few more seconds to come up with a more fitting word. He uses it again a few paragraphs later, saying that the parasitic bacteria had a mutually beneficial relationship. In this case a better word would have just been symbiotic. Neither of these examples are really big deals, but still considering the topic of the book, it probably would be good if he got his biological terms right. 1. Callaway, Ewan. "'Junk' DNA Gets Credit for Making Us Who We Are." NewScientist. 19 Mar. 2010. Web. 11 June 2010. .

Excerpt
"let's take a look at the broader connection between evolution in the animal kingdom and evolution in the plant kingdom. We'll start with breakfast. You see that strawberry in your cereal? the vine it came from wants you to eat it" (77)

This quote relates to the theme of interdependence in nature. There are almost no organisms that can survive completely independently and without any “help” from another type of organism. The strawberry is no exception. The strawberry plant is an angiosperm, meaning it reproduces by forming a zygote. Along with the zygote, the union of a plants sperm with the two polar nuclei that form along with the egg from a triploid endosperm. This endosperm becomes part of the seed coat, which will nourish the seed as it grows. The ovary of the flower will sometimes form into the fruit, and in the case of the strawberry plant, this is the strawberry. However, the plant has problem because even though it has made the seeds in order to ensure a next generation of strawberry plants with the parents genetic information, it has no way of ensure that those seeds get anywhere. Humans are heterotrophic, meaning we cannot make our own energy and nutrients; we have to get them from an outside source. We do this by consuming fruits, grains, and other animals. Our digestive system goes to work, and in the end we come out with a good supply of glucose, amino acids, and vitamins, which serve as coenzymes for many processes. By cellular respiration, we can use that glucose to form ATP and by transcription and translation, we can make our own proteins from those amino acids based on what our DNA tells us we need. However, if we don’t have the sources of energy and macromolecules we need for all this to happen, we’re in big trouble. This is where the interdependence comes in to the nature. So its been established that humans need the strawberry, and strawberries need the human. Now I realize that these aren’t the best examples considering humans don’t really get anything from strawberries that they couldn’t get anywhere else, and humans aren’t the ideal animal for spreading seed because of the whole we live in houses thing, but just for argument’s sake you can pretend that the strawberry represents any plant that provides an animal with nutrients, and the human represents any animal that walk around and eats plants. So how does each ensure that it gets what it needs from the other? Well as Moalem describes in the book, strawberries have developed mechanisms that make it so it can only be taken when ready, like not falling off the plant until ripe, but there are others, like having a good taste. It could be suggested then that humans evolved the ability and the pleasure at tasting sweetness to ensure that we eat things like strawberries, and thus consume enough glucose. If this were true, it would mean that not only does interdependence in nature exist, but also whichever organisms are involved in the dependent relationship are completely aware of it, and actually behave or develop differently to ensure that the relationship continues. I think it was really interesting that Moalem chose to discuss plants in the context of a relationship like this. Often times we only think of animal-to-animal symbiotic relationships, or in the case of parasites, microbe to animal. Its good that he talked about plants, because I don’t think we give plants enough credit, not only for the good they do us, but also for the tricks they play on us. On that note however, it could be argued that he gives them a little to much credit, even using the word “want” in this quote, because its not really true that the plants are “thinking” this all through, Again though, this could just be a tactic used to try to convey a complicated scientific issue to the masses, and he really means to say that plants that detached fruits when they were ripe led to the seed being spread around so effectively that they became the norm through evolution. Sometimes it is easier to think of things like this in terms of like and want, but that can get confusing once you try to really learn the topic scientifically. Either way, it’s a really interesting concept, and one that should be researched more, so we can find out what’s really happening in those little plant “brains”.