A mutation is the changing of a gene’s structure, resulting in a various form that may be passed down throughout generations, that is caused by the change of single base units in DNA, or the deletion, insertion, or substitution of larger sections of the genes or chromosomes. Insertions are extra base pairs that are added, deletions are base pairs that are removed from the DNA, substitution is when a base pair exchanges one base for another. A type of genetic disorder is called clinical depression, which is also a mental disorder.Depression is known as a genetic, mental, and mood disorder that causes a constant feeling of extreme sadness and loss of interest in what a person used to consider fun. Depression is a disorder that ranges from mild to extreme. Clinical depression, which is also known as major depression or major depressive disorder, is a more severe type of depression. The first symptoms of depression that were recorded, were by a Greek physician, Hippocrates, which was written somewhere between 460-370 BCE, which during the time it was called and classified as mania, melancholia, and phrenitis. In modern day, depression is now classified as its own mental disorder. Some symptoms of clinical depression are: feelings of sadness, emptiness, irritability, frustration, loss of interest in most or all fun activities, insomnia, sleeping too much, fatigue, loss or increase of appetite, anxiety, agitation, restlessness, slowed thinking, speaking, body movements, worthlessness, guilt, trouble thinking, trouble making decisions, trouble with memory, having frequent or reappearing thoughts or attempts of suicide, physical problems that happen for no reason. These are the symptom criteria for major depressive disorder in the “Diagnostic and Statistical Manual of Mental Disorders”, which is published by the “American Psychiatric Association”, that are used by doctors.The chromosomes that cause or are or may be linked to clinical depression are chromosome 11, chromosome 15, chromosome 15, chromosome 3, chromosome 2. The genes that are or may be linked to clinical depression are the genes 5HTTP/SLC6A4, APOE, DRD4, GNB3, HTR1A, MTHFR, SLC6A15, and SLC6A3.The World Health Organization estimated that 10-15% of the general population will experience clinical depression during their lifetime, 5% of men and 9% of women will experience a depressive disorder in a given year. Women have doubled the chances of having depression compared to men. Clinical depression occurs in all ethnicity and age groups. The age group that clinical depression occurs the most in are teenagers to young adult.Treatments used for clinical depression are medication selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, atypical antidepressants, tricyclic antidepressants, monoamine oxidase inhibitors, and other medications. Other than antidepressants psychotherapy, electroconvulsive therapy, transcranial magnetic stimulation is used to treat depression.Not only is clinical depression a mental and mood disorder, it is also a genetic disorder. Clinical depression is not only caused by outside factors, it can also be passed down from generation to generation.