Fred has an extremly rare autosomal recessive disease, so what is the chance that both of his grandfathers are carriers? our teacher said this homework assignment involves hardy-weinburg equilibrium but we are pretty sure this is not one. can someone us out and explain the answer even if it is not hardy weinburg

The answer is is 50% because if the disease is a recessive trait, his grandparents could've gotten the gene of the disease from their parents, so its 50-50 chance that his grandfathers are carriers, but it mostly depends on what genes their mom and dad gave the grandfathers, and then they probably passed the gene on their kids, and then their kids passed the gene onto fred, and he ened up with the disease. 

hopefully this helps you