What is the purpose of a gene

Genes are a set of instructions that determine what the organism is like, its appearance, how it survives, and how it behaves in its environment. Genes are made of a substance called deoxyribonucleic acid, or DNA. They give instructions for a living being to make molecules called proteins.

Explanation:

Genes tell your body how to make all its proteins. Each new cell in the growing embryo receives a full set of genes. But not every cell needs to make every protein and cells make some proteins only at certain times. Some genes are instructions for proteins that regulate the activity of other genes.