We have found that strain CC-421 of C. reinhardtii yields aberrant sex
ratios in genetic crosses: many tetrads emerge that are 3 minus: 1 plus
and some are 4 minus: 0 plus. This outcome is caused by the presence of
an extra copy of the minus-dominance (mid) gene, normally single-copy in
the mt- locus, translocated to some other chromosome in the CC-421
genome; CC-421 is mt- in any case, but when it is crossed, mt+ cells that
also inherit this autosome are converted from plus to minus. The "421
element", moreover, is often lost from the plus/minus meiotic products as
they divide, generating clones that are functionally homothallic.
We are writing this material up for publication, and it occurs to us that
conceivably someone has in the past noticed this phenomenon, either in
the 421 strain itself or, even more interesting, in some other strain.
If this rings any kind of bell, however indistinct, we would very much
like to hear from you. Thanks!
Patrick Ferris, or
ursula at biodec.wustl.edu