A protein is a large sequence of amino acid that was translated in ribosomes (or rough endoplasmic reticulum) from a mRNA that was transcribed in the nucleus from DNA. If the protein has an extracellular function (like immunoglobulin) if should be exocytosed from the cell. The protein in the cell is driven to the membrane into vesicles that have a specific receptor, which allows, while in contact with the inner side of the cell membrane to open it and let the protein being transported in the extracellular medium.
A gene is a small section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein. It is the unit of heredity, and may be copied and passed on to the next generation.
Explanation: Without gene duplication, mutation of genes would not exist. This would prevent organisms from adapting to their environment, making survival much more difficult if not impossible.