Genetics is the study of how traits are passed from parent to offspring from one generation to another. Genetics is one of the central tenants of biology and it shows up again and again in other areas of biology.

The study of hereditary traits has been around in one form or another for thousands of years. The earliest observations included selectively breeding animals to present desirable traits through a process called husbandry. Later we see civilizations selectively cultivating plants to yield greater harvests in a practice called selective breeding.

The two biologists given the most credit for the composition of gene theory are Charles Darwin and Gregory Mendel.

In 1859, Charles Darwin in his book, Origin or the Species, recognized that animals have the ability to adapt to their environment. Over several generations characteristics developed presented themselves that made the animal more suited for its unique environment.

 

(it is worth noting that recent study in genetics has reinforced these observations of natural selection and adaptation however challenge the derived Theory of evolution (Or Macro adaptation), if your interested in these studies starting in the 1980s check out: https://www.nature.com/articles/nrg1523 )

 

In 1865, Gregor Mendel, began the first repeatable scientific experiments exploring the expression of genes in plants, thus becoming the father of gene theory. Gregor Mendel observed the flower color of pea plants over several generations and mathematically determined the probability of specific gene expression through a process called probability theory. We can visually express this theory using Punnett squares.