July 8, 1999
Genetics and Heredity
Question from Chattanooga, Tennessee, USA:
I am 16 years old and I want more information on Type 1 and Type 2 diabetes. I have Type 1 and my daddy has Type 2. I was just wondering if diabetes is a recessive or a dominant trait. And I wanted a karyotype of a diabetic and maybe you would know where to find one.
The genetic component of Type 1A (autoimmune) diabetes, the commonest form in young people, is mostly expressed by the MHC genes on the small arm of chromosome 6. The condition cannot be expressed as recessive or dominant because actual clinical development is also dependant on some as yet unknown environmental factors. The karyotype in all forms of diabetes looks normal except for the rare form of diabetes in children with Down’s Syndrome who have Trisomy 21. Some cases of Type 2 diabetes are associated with chromosomal changes; but again the karyotype appears normal. You would find a picture of a karyotype in any book on human genetics in your nearest public library and certainly if you could get to a medical library in the Genetics chapter of a book like Current Pediatric Diagnosis and Treatment by Hay and others.