The gene is a carrier of hereditary characteristics of each individual. Genes are carried on the DNA molecule, which is passed from parents to offspring. Thanks to the genes which contain all the information required to build an organism, each person is unique and unrepeatable with a set of characteristics that are formed through the interaction of the individual and the environment. This paper focuses on the role that genes play in individual differences in personality traits and cognitive functioning. Although the general cognitive ability is individually variable, it is proved to be a highly heritable trait in which the highest degree of heritability has the ability to execute attention (0.78), followed by the processing speed (0.62), verbal ability (0.55), memory (0.52) and spatial ability (0.32). Studies conducted on identical and fraternal twins have shown that genes have influence on the academic performance (approx. 40%). Looking at the impact of genes on personality traits, studies have confirmed that family members have similar personality traits thanks to genes. Environmental factors affect the short-term aspect of subjective well-being, while genes have more influence on the long-term aspect, that is the personality and stable living conditions. The impact of the environment on the character traits is approx. 58%, while the influence of genes is approx. 42%, but that does not explain how a trait is created neither which gene is responsible for the formation of that trait.