You have two copies of every gene because you inherit one copy from your mother and one copy from your father. This is called diploidy, and it's a key feature of most sexually reproducing organisms.

Here's why having two copies of each gene is beneficial:

* Redundancy: If one copy of a gene is damaged or mutated, the other copy can often compensate, ensuring the proper function of the protein that gene encodes.

* Diversity: Having two copies allows for more genetic variation within a population. This variation can be crucial for adaptation to changing environments and resisting diseases.

* Fine-tuning: Different versions of the same gene (alleles) can have slightly different effects, allowing for a finer level of regulation and expression of certain traits.

* Genetic Repair: During DNA replication, errors can occur. Having two copies allows for the use of the other copy as a template to correct any mistakes.

However, it's important to note that not all genes are present in two copies. Some genes are located on the sex chromosomes (X and Y), and males have only one copy of these genes. Additionally, some genes exist in multiple copies (gene families).

Overall, having two copies of every gene is a fundamental principle of genetics that ensures the proper functioning of our bodies and allows for the evolution of species.