What is the chance of Inheritance of diabetes?

Adult onset Diabetes(Type 2)

When one twin of an identical twin pair develops type 2 diabetes, the risk that the other twin will develop the condition is between 50% and 100%. Despite this clue to the involvement of genetics in the development of the condition, just as with type 1 diabetes, the inheritance pattern of maturity-onset type 2 diabetes is not clear-cut.
Recent research suggests that type 1 and type 2 diabetes "cluster" in the same families. These findings support a possible genetic interaction between type 1 and type 2 diabetes mediated by the HLA genes .
From work on animals, it is suggested that predisposition to develop type 2 maturity-onset diabetes may be due to inherited variations in one or more of several genes. Genes located on the long arms of chromosomes 2 (2q), 12 (12q), 1 (1q), 3 (3q) and 20 (20q) have been implicated.

Thus while research is continuing to define the genetic involvement in type 2 diabetes, the risk that relatives of a family member with diabetes will also develop the condition has been estimated from observation of families with a history of the condition.

For example, the risk for developing type 2 diabetes to the siblings of people with the condition is about 30%. When one parent has type 2 diabetes, the risk that their child will also develop diabetes in middle age is about 10 % or 1 chance in 10.

If however both parents have type 2 diabetes, that risk increases to about 20% or 1 chance in 5 and the diabetes may also onset earlier than middle age. Nevertheless, since these risks relate to the tendency or predisposition to develop the condition, diet and exercise may postpone the onset of the condition, or the diabetes may not develop at all.
Inheritance pattern in type-1(JUVENILE ONSET) diabetes is less strong.Even in persons with genetic suceptibility an environmental trigger is required.