Genes: the everyday reality behind a mysterious word
Our genes are more than 99% identical to those of other people. Why then is one person naturally a morning type while another tans faster in the summer sun? What exactly are these genes that science fiction has mystified and that became widely known through genetically modified food?
What are genes?
Genes are all around us: in the grass in the yard, in the fur of our pet dog, and in the microscopic bacteria on our skin. Humans inherit their genome, a unique collection of about 20,000 genes, from their parents. In addition, our bodies host vast numbers of microscopic bacteria and yeasts, each with their own genome. Sometimes viruses enter our bodies and hijack some of our cells, turning them into factories for their own genes. We can notice the successful takeover of our cells and the activity of viral genes through the symptoms of a common cold.
One in billions can make a difference
The human genome, meaning all of our genes, consists of DNA strands where four bases, adenine, guanine, cytosine, and thymine, appear in different sequences. Variations in sequence create a kind of code that allows the information in genes to guide our cells in building proteins or RNA. In humans, genes are tightly packed into two sets of 23 chromosomes, one inherited from the father and one from the mother. The chromosomes we inherit from our parents contain the same genes that express the same traits, but sometimes the two forms of a gene are different. Often the difference between gene variants, known as alleles, is minute, yet the effect can be significant.
For example, a gene that influences sleep length can contain a so-called point mutation, where just one of the gene’s 3,734 bases is replaced by another. This tiny change can cause a need for shorter-than-normal sleep. The mechanism of genetic testing is based on detecting these incredibly small differences with the latest technology.
Gene regulation creates differences
Although humans have the same approximately 20,000 genes in every cell of the body, not every cell functions in the same way. We see this in the different appearance of skin and muscle cells, for example. The reason is that cells regulate how genes are read in different ways depending on the cell type and the situation. This is why, for instance, under sunlight in summer, skin cells activate the production of melanin protein, and we see the change in gene activity as tanning. In some people, sunlight triggers a more active reading of this gene, which causes them to tan more. On the other hand, a different form of this gene can switch it off completely. In that case, we see the absence of the gene’s effect as albinism, meaning a lack of pigmentation in the hair, skin, and irises of the eyes.
Good and bad, but mostly neutral
News coverage often highlights the genetic predisposition to certain diseases. However, through inheritance, genes also guide our positive traits, even though our attention is often drawn to negative hereditary risks. It is also important to remember that genes guide our functions in close cooperation with our environment. They cannot directly predict the future, but they act as a kind of framework behind the functioning of our bodies. The eternal question in the natural sciences is the role of “nature versus nurture,” meaning the interaction of genetics and environment in shaping who we are.