Have you ever wondered why family members tend to look alike, or why certain disease run in families? It all has to do with heredity, which is the passing of traits from parents to offspring.
Traits can accumulate in later generations because offspring acquire their genetic information from parents. This can lead to evolutionary changes by natural selection, if the accumulated traits increase fitness.
Traits can be passed sexually, as is the case for most animals; or, they can be passed asexually, as would be the case in a bacterium undergoing binary fission.
Let’s first familiarize ourselves with some terminologies which we will use frequently in this section.