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Using his monastery's garden, Mendel established the fundamental laws of inheritance. His work primarily focused on the study of pea plants. While cultivating the plants, he was able to show that characteristics are passed from one generation to the next in predictable ways, and we now know that what determines these chracteristics are genes. He was able to demonstrate that 25 percent of the plants contained recessive alleles and another 25 percent contained dominant alleles. The remaining 50 percent were found to be hybrids. In this way, Mendel was able to identify both the Law of Segregation and the Law of Independent Assortment. He came to his conclusions after crossing thousands of pea plants, and two terms he coined "dominant" and "recessive" are still used by geneticists today.
In genetics, the Law of Segregation states that when gametes are produced, the two copies of a gene (alleles) for a trait separate - each gamete will therefore only receive one copy.
The Law of Independent Assortment describes the process by which gametes form with the alleles of different genes. These alleles join gametes independently of each other; they are not linked, although there are some exceptions to this law. In other words gametes result from a random mix up of parental chromosomes. This is why humans can have a child with blonde hair and fair skin, while also having a child with dark hair and dark skin.
Both of these laws ultimately became known as Mendel's Laws of Inheritance and describe the basic way in which traits are passed from one generation to the next. His findings were published in the paper, Experiments on Plant Hybridization.