Crossover tetrad types from the cross A m B × a + b

No conversion:aConversion at ma
Normal 4:4Aberrant 4:45:36:2
A m/m BA m/m BA m/m BA m/m B
A m/m bA m/+ bA m/m bA m/m b
a +/+ Ba +/m Ba m/+ Ba m/m B
a +/+ ba +/+ ba +/+ ba +/+ b
  • Tetrads are monitored for crossing over between markers A and B, closely bracketing site m.

  • a The Watson–Crick duplex nature of the haploid products of meiosis is indicated only for site m. In the 5:3 and 6:2 tetrads, conversion has been arbitrarily indicated in favor of the mutant marker. In the text, 5:3 and 6:2 indicate combined frequencies of conversion without regard to whether the conversion favored m or favored +.