According to a new documentary: Hitler's DNA: Blueprint Of A Dictator, researchers have recently analyzed a sample of DNA believed to be Adolf Hitlers. The research, which took more than 4 years, was based on the DNA from a blood-covered piece of cloth taken from a couch in the bunker of where Hitler died. They tested the DNA and sequenced Hitler's genome and were able to confirm the DNA, specifically the Y-chromosome by comparing it to the blood of a confirmed male relative. This sample revealed a mutation in the gene, PROK2, which is a variant that causes Kallmann syndrome. This syndrome affects the development of sexual organs with typical symptoms including low testosterone, abnormal genital development and a lack of a sense of smell. This research is backed up by another finding of a medical document from Hitler's stay in prison in 1923 which suggested he had a condition in which a testicle fails to descend. These findings have helped answer historical questions as to why Hitler failed to have children in spite of his belief that Germans should have large families, and why he was notoriously guarded about his private life and medical records.