Other than genes, what is the other major factor that define our traits?

Another major factor that can change our traits, other then our genes, is the environment.
There is a interaction between our genes and the environment. For example, two identical twins that go through different environments end up with different personalities, even though they share the same DNA.

Besides genes, our phenotypic expression is also influenced by environmental factors. For example, genes will control a base skin color, but exposure to sunlight will darken the skin.

Give me the statements

Lacking something of the ozone layer