Cell wall organisation in Chlamydomonas reinhardi. The role of extra-nuclear systems

Among a series of mutants regulating wall formation, two exhibit both Mendelian and non-Mendelian segregation patterns on crossing with wild type. In addition each, on crossing with an identical mutant, frequently gives wild type and pseudo-wild type forms. Diploid wild types can be generated by fusing two identical haploid mutants. The results of genetic analyses indicated that extra-nuclear information is involved in the regulation of wall formation; this is usually stable in vegetative cells but can be renewed at the diploid spore stage. The degree of autonomy of the extra-nuclear system is considered, and the possibility of its being ultimately based on nuclear information discussed.