We do not know what most of our DNA does, nor how, or to what extent it governs traits. ~ English physicist and chemist Philip Ball
German zoologist Wilhelm Haacke came up with the concept of genes near the end of the 19th century. He imagined that hereditary traits were molecularly self-contained. A gene was originally idealized as a molecular unit of trait heredity.
English evolutionary biologist William Bateson coined the term genetics in 1905, from the Greek word gennō: “to give birth.” Danish botanist Wilhelm Johannsen followed in 1909, using the term genes to define dollops of inheritance information.
These concepts were concocted in anticipation of pursuing the path trod by Gregor Mendel. Researchers set their sights on discovering what they wanted to see rather than exploring what was.
In the 1950s, as molecular biology progressed, a gene was partially redefined as a template for producing a protein. As proteins are the workhorse of cellular life, the fallacious assumption that proteins were associated with heredity lingered, by virtue of their terminological association as genes. Thus, genetics proceeded upon a dogma of woolly wishful thinking.
Simplism in genetics was part and parcel of the mechanistic mindset which has pervaded science since the 17th century, when Descartes formulated the reductionism that materialists have found so appealing.
The facile notion of genes as localized trait heredity units belies the incredibly sophisticated network of knowledge involved in a cell managing its life. Hewing to the simplistic gene paradigm impeded comprehension for decades, and has only loosened in the 21st century, as understanding of epigenetics has dissolved the formulaic concept of genes.
Most of the assumptions that we operate on in molecular biology derive from the initial assumption that most genetic information is transacted by proteins. And while that’s largely true in bacteria, it’s not true for humans. ~ Australian molecular biologist John Mattick
Proteins are the prototypal gene product, but there are also innumerable DNA regions that do not code for protein, but which instead are employed to create useful RNA products. These different RNAs perform a diversity of tasks, including assisting protein synthesis and training, catalyzing biological reactions, cellular communication, and acting instrumentally in gene expression.
Genes are often described as if they are linear sequences, awaiting ready decoding as construction templates for useful products. Nothing could be further from the truth.
The DNA coding schema defies easy characterization because it defies topological comprehension. Further, workable regions vary dynamically, influenced by a variety of factors.
Hemoglobin is the iron-based oxygen transport protein in the red blood cells of vertebrates. Many different proteins go into hemoglobin, as well as other molecular constructions necessary to produce hemoglobin. The instructions for those different components lie on different chromosomes.
The example of hemoglobin highlights not only the distribution of DNA strands, but also the use of nested instructions. The formula for hemoglobin is a set of recipes for distinct components, where each component has its own template (coding sequence).
Genetic material is even more complex. The encoding represented by DNA is nothing more than the score of a symphony that is played by an orchestra, where every player contributes to the overall effect. Lacking a singular conductor, it is an interpretive exercise by a multitude. The way that template data are arrayed and move within cellular space profoundly affects their functioning.
Individual chromosomes occupy distinct territories in the cell nucleus. Where they reside, and what other chromosomes are in the neighborhood, can strongly influence whether the genetic material in a chromosome is active and how it functions.
Operationally, the gene can be defined only as the smallest segment of the gene-string that can be shown to be consistently associated with the occurrence of a specific genetic effect. ~ American geneticist Lewis Stradler in 1954
The definition of gene is non-specific for good reason. A gene is conceptual, not an actual entity: a term for the information encoded within polynucleotides. Genes don’t exist. They are only construals in the minds of geneticists.
20th-century biology was structured according to a linear Newtonian worldview. Molecular biologists were so set about linearity that when the gene came along, they took the gene to be the be-all and end-all of basic biology. That comes out of thinking in terms of particles and linear interactions. ~ Carl Woese
Mapping the notion of genes to reality has meant a constant revision of presumption. Definition of the term gene itself has been a moving target, and its meaning still varies widely. The concept itself is debased in understanding that, however the term is defined, a ‘gene’ is not functionally or structurally delimited. Theoretically, genetics is nothing more than sloppy sophistic philosophy.
The term gene is used as if the recipe and result were synonymous. They are not. Research into epigenetics has shown that genes as an adhered-to rulebook represents an inapt simplification.
However misrepresentative, the concept of genes is so ubiquitously doctrinal that it is the requisite context for introductory exposition. So we proceed.