Nature vs. Nurture

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Now that we’ve gotten the idea of queer as a verb out of the way, let’s queer the first issue in biology- that of the metaphorical nature and nurture. Most often when discussing development, people will talk about these two influences in reference to genetics and environment, respectively. The idea here is that genetics represent the immutable truth of an organism, or its true nature that can not be changed, while environmental factors, or the nurturance of an organism, are things that can be changed, and thus ways in which we can change the organism. You can probably guess the punchline here- nature and nurture are not two independent factors on the growth and development of an organism.

epigeneticsConnecting these two factors of nature and nurture is the process of epigenetic modulation. The prefix “epi-” means “above, on, nearby; outer; besides, in addition to.” Genetics concerns itself with the sequence of nucleotides and genes found in DNA. EPIGENETICS concerns not the order of the nucleotides, but the structures above, on, around, beyond, and nearby those nucleotides, such as methyl groups and histone packing proteins.

Every macromolecule of deoxyribonucleic acid (or DNA) includes three components- a deoxyribose sugar, a nucleic acid base, and a phosphate group. These individual nucleotides are joined into long strands or circles, and then paired with a complementary strand of nucleotides. There are four nucleotides that make up all of the DNA in every living organism, adenine, guanine, thymine, and cytosine. The purine nucleotides (adenine and guanine) each have two rings to their base structure, while the pyrimidines (cytosine and thymine, plus uracil found in RNA only) have a single ring structure. This size difference means that one purine must always pair with one pyrimidine in order to keep the complementary strands the same distance apart from each other, and create a stable double helix. Add to this the potential for hydrogen bonding, and you have a nearly perfect system for replicating and checking that complementary strands are exact matches, with adenine and thymine forming two hydrogen bonds between them them and cytosine and guanine forming three.

0322_DNA_Nucleotides

Our genes are our genes and are not changeable in an organism with today’s technology (although CRISPR technology is getting us closer to that possibility), that is an accurate assertion from the nature camp. However, there are many, many environmental factors that can change the epigenetic super-structure of DNA, and by doing so alter the expression of those genes. For example, stress as measured by cortisol level has been shown to cause methylation or de-methylation of various genes, making those genes easier or harder to transcribe. Other environmental factors causing epigenetic shifts include disease exposure, diet, day-night cycles, interactions with other organisms, and temperature.

Epigenetics is the tie that binds both nature and nurture. Our genes determine what types of proteins we are capable of producing, and our environment alters the expression of those genes. This isn’t a dichotomy so much as a codependence. To add another layer to the cake, our life history and development as determined by the interaction of our genes and environment further influence what we are capable of doing during adulthood. By this I mean that as we develop, the structures formed as our body grows may not be constantly able to respond to new environments in the ways that they were able when we were younger. Even with genes for extreme height, if given inadequate nutrition, a child will not grow to their full potential. Correcting that nutritional deficit in adulthood will not cause that adult to grow further to the size that might have been dictated by their genes because their bones have already been formed and stopped growing, which is an irreversible process without medical intervention, in this case in the form of physically breaking and lengthening the long bones in an excruciating, time-consuming, and expensive procedure. Both nature and nurture work together to create the end product, and this is true for nearly all traits in humans. Add to this the fact that most traits are polygenetic, or involve multiple genes, each with their own regulatory processes, and the possibility for variation and interaction between genetics and environment are nearly endless.

So please, drop the nature versus nurture charade; it’s nature and nurture or bust.

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