Answer: expression
Step-by-step explanation:
The gene expression is a process by which the information encoded in gene is utilized to produce a functional gene product for example protein. The expression of genes in organisms is influenced by the environment including which influences the release of factors due to gene expression like proteins or hormones which can further influence the physiology of the living being.
The gene expression can also influence the psychology of the living being. Certain genes are expressed when the organism suffer from external stress or tension and the organism will experience the stress internally. Thus due to external environment internal environment of living being is affected through gene expression. But when the external environment is free from stress the person will remain calm as the genes for stress will remain passive.