The Gene

Lesson 1. The discovery and evolution of genes.

Early research into the gene began in 1864, when an Australian botanist Gregor Johann Mendel performed an experiment on plants. Mendel noticed some astonishing results. While breeding those plants, some specific traits of the parent plant were always passed on to the next generation of plants. The other traits however were unique and different from those of the parent.

A tall plant, for instance, when crossed with a dwarf plant, would produce only tall offsprings, which might indicate a blending of parental traits. In plants, tallness is a dominant trait, which means it overrides the trait of dwarfism. In other words, what Mendel discovered is that hereditary knowledge, such as the characteristic of tallness, is passed down in indivisible units from generation to generation. Mendel had revealed the tiniest building block of heredity, the gene, in defining these indivisible units.

Some years later, Mendel's earlier work was revived by the Dutch botanist Hugo De Vries, and he was able to combine his theories on genetics with the theory of evolution by Charles Darwin, published when Mendel was still in school. 

Darwin suggested that all animal species had descended from earlier types of animals through a mechanism of gradual, continuous transition, rather than being a direct gift from God. The inherited work of Mendel perfectly complemented Darwin's theory. If, as Darwin proposed, a species evolved, it would make sense for an animal to transfer physical characteristics through genes.

Lesson 2. Traits and Genes are connected.

An essential question about heredity in a species was answered by the discovery of the gene. But due to this, new questions too have emerged. Researchers recognized that genes existed, but did not understand what a gene looked like or how it operated at a biological level.

Scientists have now identified the building blocks of genes with the discovery of DNA. The traits Mendel had observed so long ago literally exist on the many DNA strands of an organism. Interestingly, to transmit a trait in an organism, genes function together. Observable features, such as height, are not the product of a single gene, but rather of several genes working together.

You can think of gene expression as the interaction of pixels on the screen of your smartphone. Although each pixel is separate, they form a complete image together. Similarly, genes function independently, but when they combine, a complete picture of an observable feature in an organism is created. However, gene expression should not automatically be related to observable characteristics, such as the size and shape of the