This is my anthropology essay #1, based on lecture notes and articles.
Biological factors may influence both morphological and behavioral traits. DNA has a simple structure that can be modified through epigenetic processes, directs protein synthesis, and has a direct impact on an organism’s morphology. Neurons communicate through neurotransmitters, and these chemicals can influence behavior. Hormones are a slower form of intercellular communication but also impact behavior. Understanding the biological foundation of our actions provides a stronger sense of what unites us as humans.
The simple structure of DNA is modifiable with epigenetics and impacts the morphology of an organism. DNA is a molecule that holds hereditary information in unique non-random sequences of genetic code. It serves as a manual for most human cells in our body. Each of the twenty-three pairs of chromosomes in the cell’s nucleus consists of DNA coiled around histones, that serve as spools for wrapping tightly the very long DNA strands. Histones are the eight-protein bundles with a four-over-four shape as if they were filling up eight segments of a cube. DNA itself is shaped like a twisted ladder, in which nucleobases create the rungs, and are bonded to the sugars of the sugar-phosphate rails. All coding is made using only four nucleotide monomers: A, C, T, and G (Miller 9/6/2022). Their symbols are defined by the distinct nucleobases: Adenine, Thymine, Guanine, and Cytosine (DNA site). Complementary base pairing serves for the consistency in the nucleotide sequences: A is bonded to T, and C to G, and they tend not to snap together in other combinations. Each base has at least one hydrogen bond donor and one acceptor. Additionally, C has the second acceptor, and G has the second donor. DNA is billions of bases long (Miller 9/6/2022). The genome is the sequence of nucleotides of all DNA, and a gene is only a segment of DNA (DNA site). The structure of DNA can be modified through epigenetic processes, a more immediate form of response to the changing environment that regulates gene expressions. Cells in an organism have more or less the same set of instructions, most of which are turned off for specialization (Miller 9/2/2022). This is accomplished by epigenetics marks, an additional information layer on the sequence of DNA (Epigenetic site). Histones have multiple “tails” that serve as poles for these marks. In order to change the DNA functionality in response to the environment, histone modification is accomplished: epigenetic “tags” are attached to these tails and changed as needed. These tags dynamically regulate how specific parts of the code must be processed. Upregulation makes DNA more accessible to the proteins that are responsible for the activation, and downregulation reduces the accessibility of DNA, which is achieved by loosening or tightening the wrapped DNA areas accordingly. Methyl groups can be added outside of DNA as tags to shut down protein production. They tag only C-nucleotides that are followed by G (Miller 9/2/2022). The tags leave the signs for the special proteins in the cell to process the segment of DNA in a special way. Some epigenetic markers can change during a lifetime with exposure to external influences; some can even be inherited. (Epigenetic site). Biologists studied the influence of nutrition on mice by feeding two different diets to identical baby mice from birth. Mice that received food rich in folic acid were healthy and brown, and the rest were overweight and yellow. The protein Agouti caused the problems. It was produced in the mice on the deficient diet because of one flawed gene that was not shut down by folic acid, a methyl group that comes with the nourishment. A small epigenetic marker like this vitamin can dramatically impact the traits (Carmichael 2007). The structure of DNA together with epigenetic modifications that mediate between the code and the environment define together the personal characteristics of organisms.
One of the main functions of DNA is serving as a template for the production of proteins, affecting the characteristics of an organism. Proteins are functional molecules that act as structural support, pigments, enzymes, hormones, receptors, and neurotransmitters. Each gene contains directions for constructing specific proteins or their parts (Miller 9/6/2022). In order to produce a protein, the DNA “ladder” separates in one segment along its “rails” by separating its nucleobase “rungs” (Miller 9/6/2022). The synthesis of proteins in the cell includes two steps. First, the transcription takes place: the gene is expressed into RNA on one side of the uncoiled portion. The “reading” of the base sequence is made by DNA polymerase, an enzyme that builds the chain of the RNA molecule. The pairing is similar to that of nuclear bases, except instead of T, uracil (U) goes over A. After transcription, the modified mRNA exits the nucleus and attaches to the cell membrane. In the second step, translation is accomplished by three types of RNA: mRNA, rRNA which aids with ribosome formation, and tRNA which brings amino acids. Each RNA codon, the three-nucleotide sequence, is translated into one amino acid, but some require several codons. The ribosome processes the code triplet by tripled, starting from a non-coding stop-sequence, tRNA attaches amino acids to mRNA and to each other until the stop-sequence is reached. After the primary structure of the protein is made, all the RNA are either reused or recycled. The secondary and tertiary structures of the protein form by folding into a three-dimensional shape, which defines the functionality (Protein site). Any malfunction in protein synthesis could lead to serious changes in traits. Two teams of researchers investigated genetic disorders by studying cells under a microscope and discovered a rare mutation in the gene LMNA responsible for Hutchinson-Gilford progeria syndrome. This gene in the nucleus of a cell encodes for a protein lamin A. The mutation impacts the transportation of this protein, which results in the accumulation of its unusual form, progerin, similar to such aggregation of it in normal aging skin. Indeed, the skin of children with progeria becomes less elastic, they look much older and have weaker bones. Thus, the change of the exact sequence just in one gene can significantly impact morphology (Bhattacharya 2011). Understanding the process of protein production helps us determine and predict its effects on our morphological traits and behavior.
Neurons are nerve cells that use electrical and chemical signals like neurotransmitters to process and spread information, therefore affecting our behavior. Neurons consist of the cell body, the long insulated by myelin axon that divides towards the end, and the shorter branched dendrites (Miller 8/30/2022). The connection between the neurons takes place in synapses, the small gaps between the ends of axons, or terminals, of a presynaptic cell and the ends of dendrites of a postsynaptic cell (Neuron site). Vesicles are specialized containers in the axon terminals (Miller 9/1/2022). Neurons use electrical signals to transmit information within the cell, and chemical signals to communicate with other neurons. The synaptic process of intercellular communication uses neurotransmitters as chemical messengers. The cell body generates the electrical impulse, which is transmitted along the axon fiber away from the cell body (Neuron site). If the impulse is strong enough, vesicles release their contents. The stronger the impulse, the more vesicles open. The escaped neurotransmitters diffuse in the synaptic gap and try to bind to the specific matching receptors on the dendrites (Miller 9/1/2022). If enough neurotransmitters of the right type dock on the receptors, the signal travels further. These receptor interactions cause chemical or electric changes in the receiving cell. Excitatory neurotransmitters propagate the signal, and inhibitory diminish it. The lipid-protein myelin coating on the axon speeds up the transmission. Moments after binding, neurotransmitters are either returned to their vesicles or broken down by reuptake enzymes. There are about two hundred identified neurotransmitters, and all of them have unique functions (Neuron site). External factors like a good diet and enough rest and movement can increase the speed of neural interactions, but stress and behaviors like alcoholism can lower the brain activity level (Miller 8/30/2022). In one study on neurotransmitters and obsessive thoughts, researchers cited the help of genetics in identifying neural circuits in the brain of people with OCD diagnosis. They found that the primary excitatory neurotransmitter glutamate drives the neural circuit involved in making decisions for positive outcomes. Mutations in its transporter gene may cause dysregulation in the cortical-basal ganglia circuit and cause nonsensical behaviors (Moyer 2011). Neurons comprise our centralized nervous system, and their communication via neurotransmitters affects our information-processing ability, and subsequently has a direct impact on our behavior.
Hormones are slower-acting cell communication chemical signals that have an impact on behavior. Tissues secrete hormones into body fluids to travel until they reach specific cells (Hormone site). There, they attach only to the specific receptors to trigger the specified action. Each hormone can play multiple roles (Miller 9/1/2022). The human body makes about fifty different hormones. If some of these messengers are in low concentrations, others can take their role (Hormone site). In a study on ghrelin, a hormone that among others induces the feeling of hunger, researchers aimed to know how macronutrients impact food consumption in rats. They used equal-calorie infusions of sugar, protein, and fat into their digestive tract. Sugar and protein caused a drop in ghrelin in their blood by 70%, while fat reduced it only by 50%. Ghrelin concentrations then regulated their hunger and therefore eating behavior. Hormones in various combinations and levels impact our behavior in a multitude of ways.
Human behavior and morphology are influenced by biological processes in the body and by the environment. The universal simple mechanism of replication and transmission of information by DNA is enhanced by continuous epigenetic changes and allows the production of unique specific proteins, which influence our morphological traits. A single epigenetic marker like folic acid can change the expression of a gene and cause a dramatic change in morphology in mice. DNA structure serves as a template for manufacturing proteins, the functioning or absence of which determines our characteristics. A single genetic mutation in a gene that produces a certain protein like lamin A in people with progeria can dramatically impact morphology and health. Behavior is also influenced by the communication in the nervous system between neurons via neurotransmitters. For example, obsessive thoughts and behavior can be caused by improper functioning of glutamate, a neurotransmitter that stimulates signaling in the neural circuit that coordinates decision-making. Hormones produced in various tissues send slower specific messages to the cells, which eventually modifies our behavior as well. Like in the case of ghrelin, its production and blood concentrations motivate eating behavior. Our improved ability to make predictions for our collective behavior as a species and correct it by researching its biological factors may make the survival of humanity and other living beings more likely in the long run.
