Your genes are literally a part of your body. In every cell of your body (skin, muscles, white blood cells, nerve cells, etc) there's a nucleus containing DNA. Genes are sections of those tiny molecules of DNA that contain instructions on how to build and run your body. They are kind of like the programs that are on the hard drive of a computer. When you die, your body dies and is eventually broken down, including your genes. This is just like when your computer dies and you get rid of it. you may have made copies of those programs (children), but you don't make a new computer from the old one (usually). Remember, you eat food that is also made of cells. You don't reuse the genes from an apple and grow branches. Instead, your digestive system breaks down the DNA into individual bits which may or may not be reassembled into other molecules of DNA or be broken down for energy.