What is a gene?

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“Explainer: What is a gene?” by The Conversion is an article with the purpose of defining and clarifying misconceptions about the term gene. The Human Genome Nomenclature Organization defines a gene as “a DNA segment that contributes to phenotypic function.”

There are many genes on each human chromosome: about 20,000 genes encoding proteins and perhaps as many encoding functional RNAs. There is no precise number because it is hard to be sure which segments of DNA read into functional products. The Austrian monk Gregor Mendel carried out the first genetic experiments in the 1850s and he showed that distinct characteristics were inherited and encoded by genes. But he never used the word “”gene”” and neither did Darwin. It was first used in 1909 by Danish botanist Wilhelm Johnannsen to refer to determiners for precise properties of organisms.

The idea that genetic material was linear was born in 1915 by American geneticist Thomas Morgan found that some genes tended to be co-inherited. He deduced it might mean that certain genes were close together, like beads on a string. But genes were still ambiguous. In the 1940s, American physician Oswald Avery discovered and proved that an enzyme that chews up DNA, DNase, could destroy genes. It was concluded, then, that the genetic material was DNA. In 1953, James Watson, Francis Crick, and Maurice Wilkins using data from Rosalind Franklin showed DNA was found in the form of a double helix. This data helped proved that fact that DNA could be replicated.

What does carrying the gene for breast cancer mean? It doesn’t mean a special gene has evolved with the function of causing breast cancer. It means a gene made for limiting cellular doubling in breast tissue or in DNA support is mutated and no longer functions. So the chance of cancer growth is increased. The gene predisposes the carrier to cancer – it doesn’t cause it. The gene for hemophilia is not there to cause bleeding; it’s a gene that, when mutated, results in a defective clotting factor and bleeding is the result. There are several genes for breast cancer and there are two common genes for hemophilia. The most confusing thing is that the “gene for breast cancer” may have an indirect relationship to the biology of the breast.

With the discovery of new information and the creation of new technologies, humans can improve their knowledge of the vast genomic wonderland and discover new unknown genes.

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