Tests of 4 controlling-element systems of maize for mutator activity and their interaction with Mu mutator

The maize mutator system, Mu, behaves in a non-Mendelian manner that may be expected if it were an extremely active controlling-element system. To test this hypothesis, the maize controlling-element systems, a---dt---Dt, Ds---Ac (= MP), I---En, and r---cu---Fcu were tested for mutation activity. Ds---Ac and r---cu---Fcu tests were the only ones in which new mutants were induced, but at a frequency much lower than that found in Mu crosses. The mutation frequency in these controlling-element systems does not differ statistically from that found in control (Non-Mu) populations.

Tests also were made to determine if Mu will substitute for the regulatory element of any of the 4 conotrolling-element. All tests were negative, suggesting that, if Mu is a controlling-element system, it is a different one from those previously described.