B Cells, T-Cells, Hemoglobin

Biology

B and T cells are both types of white blood cells, and are the only nucleated cells of the body that lose DNA during development and maturation. This is due to a process called somatic recombination or V (D)J recombination, which introduces an element of randomness to the process of cell formation and maturation, by putting together one of each of three types of gene segments (Variable, Diverse, and Joining, or VDJ) but not incorporating more than one of each. As a result, the cells can end up having about 300 billion different randomly-generated gene sequences, all of which are fundamentally shorter than the ordinary DNA sequence. There are several important things to note about how this process relates to DNA's role in human biology overall. For a start, this is clearly an adaptive advantage: B. And T cells are generated in the bone marrow (and T cells mature in the thymus) but their primary function is to defend against antigens. As a result, the vast number of different types produced during VDJ recombination provides an enormous repertory of different defenses. Moreover, it is possible for the body to essentially clone different types of these cells based on what type of defense is required: in fact the body will store a small amount of "memory cells" so as to essentially retain some method of cloning certain combinations that have been useful in the past. What this does is provides a tremendous adaptive advantage against potential threats to the system: the randomness is, however, a "double-edged sword" insofar as it creates non-viable possibilities (Murphy 2011, 264). As a result, the maturation process includes a test of functionality, and non-productive combinations may be subjected to further gene rearrangement. Overall, this indicates DNA's value in encoding heritable biological information: the inclusion of different possibilities within that information to maximize survival strategy is certainly the goal of this unusual form of DNA transcription here.

2. What Kara Goucher is doing artificially with the tent is essentially the same thing that she could achieve naturally by going to the top of a mountain, where the amount of available PO2 is automatically lower, so as a result both of her endurance training regimes are based around the same basic biochemistry. Deliberately reducing the amount of PO2 circulating in the breathable atmosphere around a person -- such as Kara accomplishes at sea-level with her tent -- ultimately produces a lowered rate of hemoglobin oxygenation in the arterial blood. This condition, hypoxia, can be dangerous and can, of course, impair aerobic physical exercise -- however the trick that Kara is taking advantage of is the body's ability to undergo acclimatization, in which the body's physiology and metabolism will engage in adjustments that improve the body's ability to tolerate the low-PO2 levels through different means, such as adjusting its own acidity (to change the level of interior biochemical reactivity in order to boost absorbable oxygen levels) but also -- more importantly for Kara and her endurance training -- by improving metabolism on the cellular level and blood circulation (to maximize the value of the oxygen actually obtained) and, most importantly, by "increased synthesis of hemoglobin and red blood cells," thus increasing the amount of oxygen that can be captured and used in Kara's arterial blood (McCardle et al. 609). Oxygen, of course, binds to the iron in hemoglobin and is then transported throughout the body to be used -- Kara's interest is its use by those muscles most heavily used in her running. As a result of this training, when Kara comes into the more PO2-rich atmosphere of New York City for her marathon, she will have trained her body to extract more from the available oxygen in the atmosphere (mostly from the hemoglobin boost but also from the metabolic, circulatory, and acidity adjustments), and thus permit her to exercise with a higher level of endurance.