Ser or Bd[S]

Steve Henikoff steveh at
Wed Jan 12 18:21:42 EST 1994

Dr. Alan Christensen writes:

>P.S. I'm not going to tackle Pm vs. bw[V1].

Muller originally reported second chromosome eye-color dominants which he 
called Plum mutations apparently before he realized that they were allelic to 
brown (bw) recessives (Pm/bw- is more extreme than Pm/bw+). bw[V1] is
the only surviving allele originally referred to as "Plum" for which this 
designation persists, so it is commonly called Pm without an allele number.
But it is only one of many dominant brown variegated alleles, some of which 
are also in common use, such as bw[VDe2] and bw[D], so a special name for 
this particular allele seems unnecessary. I think the reason the name has 
stuck is that bw[V1] has two inversions with breaks near both tips and is 
lethal, so therefore Plum can serve as a balancer for much of the second 
chromosome. Being viable over better balancers carrying Curly, Plum is 
especially useful because by crossing to Cy/Pm, all progeny are typically 
balanced and marked with an obvious dominant marker, not just half. It seems
most appropriate to me to use Plum or Pm in reference to the chromosome (such
as in referring to the widely-used "Curly-Plum" stock) which carries the 
bw[V1] allele.

--Steve Henikoff

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