Help on genetic problem... AS SOON AS POSSIBLE?

As you stated, color blindness is linked. That is, the gene is carried on the X chromosome. The most likely scenario is that Dave's grandfather was color blind and he ped the gene to Jake's mother. Judith most likely has two normal X chromosomes, since none of the children are affected. Is there a chance that she could be a carrier? Yes, with the same odds that a flipped quarter will come up heads twelve times in a row. I've forgotten the statistics.