No, there is a type of diabetes called MODY which may be misdiagnosed as T2 or T1 and is caused by an autosomal dominant mutation .
http://en.wikipedia.org/wiki/Maturity_onset_diabetes_of_the_young
The category T2 probably covers more than one type.
That said there are many gene variants that have been associated with people who have the condition. It is thought to be a polygenic (ie influenced by several genes, each individual allele variation seeming to cause only a small increase in risk). If you have many of these gene variations you might be thought to have a higher risk than those with fewer of them. However, whether you develop it is influenced by the environment as well.
A very recent paper looked at a large group of people from several
European countries* and genotyped them for 49
known variants that are associated with T2. They divided them into groups from low to high genetic risk (ie those with most susceptible gene variants would be in the highest risk group)
These were followed for an average of nearly 12 years. They looked for various interactions ie BMI, diet, physical exercise, family history etc
By far the biggest gene/environmental interaction was obesity. Basically those who had a high risk phenotype but were of normal BMI didn't have a much bigger risk of developing T2 during the period. Indeed, those with a low risk phenotype but high BMI developed it more frequently than the those who had a high risk genotype but were of normal BMI.. (that's hard to put clearly!)
.
http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001647
Have a look particularly at figure 4. (click on it to make it bigger)
But genetic research is still somewhat in it's infancy, the findings here may well be modified as we learn more about genetics and epigenetics.
*They didn't look at gene variants know to exist in Asian populations so this research doesn't have any relevance to this group .
