Educating judges and others in the court system about the nature and implications of genetics, including its limitations, is very important. Most judges are not and never have been scientists, so they are inhibited and uncertain when scientific matter is entered as evidence in a trial. Diabetes mellitus is a good example of a complex disease. We also know that in genetically identical twins, when one twin has diabetes, the other twin has only a 1 in 3 chance of developing the condition. So there is a 2 in 3 chance that the other twin will never get diabetes, even though the twins have identical genes.
Environmental factors involved in susceptibility remain to be elucidated.
But even understanding a simple, single-gene disorder presents many challenges. Some alleles may give rise to the full-blown, fatal disease, whereas others apparently have little or no effect on the individual. Commercial gene tests available now present problems for doctors and patients in understanding the implications of a positive test, particularly when used prenatally. More research will be needed to determine the effects of each variant allele. More than 250 alleles are associated with two genes called BRCA 1 and BRCA 2, which can cause a rare, inherited form of breast cancer.