22q11.2 deletion syndrome is caused by the deletion of a small section of chromosome 22. It results in a cleft palate, heart defects, autoimmune disorders, and more. The symptoms vary wildly and can be accompanied by learning disabilities and mental illness. Cystic fibrosis is caused by a point deletion.
The melody of Happy Birthday to You comes from the song  Good Morning to All , which has been attributed to American siblings Patty Hill and Mildred J. Hill in 1893, although the claim that the sisters composed the tune is disputed.
The sisters used Good Morning to All as a song that young children would find easy to sing. The combination of melody and lyrics in Happy Birthday to You first appeared in print in 1912, and probably existed even earlier.