The genome is the set of all genetic material, that is, all the DNA, found in a living being. An individual's genome contains enough information to develop a functional copy of themselves and their subsequent development. Despite common belief, the genome is not only the DNA found in the cell nucleus, but also includes the DNA of the organelles contained in the cell, such as the mitochondria in humans. In the case of humans, generally each of the cells carries the same DNA and, therefore, an exact replica of the individual's genome.
In the human species, the genome in cells is found in duplicate, except for the sex chromosomes in males, as we are diploid organisms. Each of the two copies comes from one of the parents. Because of this, there are diseases in which an individual can be a carrier of the gene for the disease without manifesting it. These are called recessive diseases, which require both copies of the gene to be defective to develop. Conversely, for a dominant disease to be expressed, it is sufficient for one of the two genes to have the altered information.