grown an1 seedlings the basis of the reduced height lies in the cells of the mesocotyl coleoptile cell number is slightly reduced in an1 seedlings while the average cell length of coleoptile cells is the same as found in wild type siblings table 1 this is in contrast to the mesocotyl where cell number is reduced by one half and average cell length is reduced to one fourth of that observed in wild type seedlings thus the reduced stature in dark grown seedlings is due primarily to greatly reduced final cell lengths table 1______________________________________comparison of cell length and cell number in shootsof dark grown maize seedlings number of average cell length length mm cells mm ______________________________________tall siblingcoleoptile 18 228 0 08mesocotyl 70 294 0 18total 88 522dwarf an1 coleoptile 14 171 0 08mesocotyl 6 130 0 05total 20 301______________________________________ seedlings were grown for six days in total darkness the an1 gene was cloned using transposon tagging a key advantage for tagging genes with mutator is the 50 fold or greater increase in mutation frequency compared to spontaneous rates see walbot 1992 for a review transposon tagging involves using any one of a number of naturally occurring plant transposons mu ac spm and the like to create a 34 molecular tag 34 to recover the mutated gene although it has been used before the transposon tagging approach to recovering a gene of interest is unpredictable is plagued by a low mutation frequency and is very difficult technically first the genetic stocks have to be screened phenotypically for mutants of interest there is no way to.