In humans there are 23 pairs of chromosomes, or 46 single chromosomes in all cells of the body except the sex cells. Please refer back to the picture you just looked at. The sex cells are often called Gamete cells, the regular body cells are called Autosomes . Chromosomes which are in the nucleus of a cell, provide the code to make protein which will build , repair , or reproduce any cell within a living organism.
Genes are the smallest chemical parts that form segments of chromosomes.
Damage or error can cause normal aging of all living organisms. This is actually a little extreme for this to happen since mutation of a gene usually causes cell death whether in Meiosis or Mitosis. There are many genes we have that are not expressed. There are some humans born today that still have a small bud for a sixth finger which is usually surgically removed at birth. All humans at sometime before birth have webbing between the fingers and toes.