Further evidence for the Indian origin of the Roma came in the late 1990s when it was discovered that Roma populations carried large frequencies of particular Y chromosomes (inherited paternally) and mitochondrial DNA (inherited maternally) that otherwise exist only in populations from South Asia.
47.3% of Roma men carry Y chromosomes of haplogroup H-M82 which is otherwise rare outside of the Indian subcontinent. Mitochondrial haplogroup M, most common in Indian subjects and rare outside Southern Asia, accounts for nearly 30% of Roma people. A more detailed study of Polish Roma shows this to be of the M5 lineage, which is specific to India. Moreover, a form of the inherited disorder congenital myasthenia is carried by around 4% of the Roma population. This form of the disorder, caused by the 1267delG mutation, is otherwise only known in subjects of Indian ancestry.
This is considered unambiguous proof that all Roma are descended from a single founding population, originating from the Indian subcontinent around 40 generations ago, which subsequently split into the subgroups we see today.