Pos for 2 copies of g20210a. parents tested neg.how is that possible? i have 1 copy of factor v leiden & dad has 2 copies.mom has a blood clot in leg.

Prob error in test: May be test error in you or Mom. Likely that Dad has transmitted F V Leiden to you as expected. Either he or your Mom likely also has F II (20210A) mutation- guess would be your mom due to her blood clot. Possible you are a new mutation for 20210A but very very rare and unlikely. Other possibility is non-paternity or non-maternity.

Interesting: For you to be homozygous(having two abnormal copies) for the prothrombin 20210 gene then both of your biologic parents had to have at least one copy of the abnormal gene. You inherit one copy of the prothrombin gene from your mother and the other from your father. So while your biologic parents may not be "homozygous" they must at least be "heterozygous" for the 20210 gene.