The study of heredity goes on in laboratories all across the world. But scientists won’t tell you they’re researching heredity. They prefer to talk about “genetics.” It all started with a European monk by the name of Gregor Mendel. Based on consistent patterns he observed in heredity, Mendel correctly guessed that a kind of unit of heredity was transferred from parents to offspring. This discovery eventually led the scientific community to find that unit of heredity: the gene. Understanding the gene is the key to understanding genetics.

The study of heredity is fairly new, and for good reason. While people in the past noticed clear similarities between parents and children, both in humans and animals, they had no real way of “looking inside” the mechanism that created these similarities. At the outset, the study of heredity was chaos. Every scientist had his own idea about how traits were passed from parent to child, mainly because science lacked a consistent way of talking about heredity. They lacked the “unit” of heredity.

It was only after the Austrian monk Gregor Mendel began running scientific experiments on heredity that the study of heredity became a real science. Mendel discovered basic rules of heredity through experiments with the green pea plant. His results answered many questions on which scientists at the time had failed to gain consensus. For example, he showed that both parents equally contribute to the traits of their offspring. But most importantly, through Mendel's work, he inferred the existence of the gene.

Once scientists understood the importance of Gregor’s work, they defined the gene as the basic unit of inheritance, according to Alfred Sturtevant, the creator of the first genetic map of a chromosome and author of “A History of Genetics.” A gene is to heredity what a number is to math. Without one, you cannot discuss the other. Today, when scientists talk about heredity, they discuss it in terms of genes. This is why the study of heredity is called “genetics.”

Scientists in the field of genetics are still in the process of fully understanding how heredity works. Simply knowing the unit of heredity is not the holy grail of the study of heredity. Understanding the existence of different versions of genes, known as alleles, can help scientists calculate the probability of certain factors of heredity, such as the probability of having a child with blue eyes or inferring your ancestors’ origins. However, the sheer number of genes and the problem of determining how they work together to create traits leave scientists with much more work to do.