The 46 human chromosomes (22 pairs of autonomies and 1 pair of sex chromosomes) between that house nearly 3,000 million base pairs of DNA containing about 80,000 genes that encode proteins. The coding regions occupy less than 5% of the genome (the function of the rest of the DNA remains unknown), some chromosomes having higher density of genes than others.
One of the biggest problems is finding out how genes contribute to the complex pattern of inheritance of a disease, for example the case of diabetes, asthma, cancer and mental illness. In all these cases, no gene has the potential to determine whether a person will develop the disease or not.
Little by little they are aware of some diseases whose cause is the alteration or mutation) of all or any region of a gene. These diseases usually affect all body cells.
