Based on the research and studies in the field of genetics and alcohol dependency, we know that there are various factors that can contribute to a person's susceptibility to alcohol dependency. These factors can include environmental influences, psychological elements, and genetic predispositions.
Specifically focusing on the genetic aspect, significant research has been done to quantify the contributing factor of genetics to alcohol dependency. While genetics is not the sole determinant of alcohol dependency, it does play a substantial role.
Between the different percentages given:
- [tex]$25 \%$[/tex]
- [tex]$50 \%$[/tex]
- [tex]$75 \%$[/tex]
- [tex]$100 \%$[/tex]
After thorough evaluation of the data, it is understood that around 50% of a person's genetic background may contribute to alcohol dependency. This means that genetics can be considered a strong contributing factor, but it is not the only factor involved in alcohol dependency. Environmental and psychological factors also play critical roles.
Thus, the correct answer is:
[tex]$50\%$[/tex]