Which of the following can be inferred from the Beadle and Tatum experiments?
a) For a mutation resulting in the production of a defective enzyme involved in a biosynthetic pathway, the compound preceding the corresponding step will accumulate.
b) A given Neurospora mutant can be deficient in either a vitamin synthesis pathway or an amino acid synthesis pathway, but not in both.
c) Neurospora vitamin auxotrophs do not require amino acids in order to grow.
d) X-ray-induced mutations are confined to genes encoding enzymes.