Worm Breeder's Gazette 9(2): 44

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Observations on Strains with High Tc1 Copy Number

J. Hodgkin

In order to identify Tc1 polymorphisms close to the sex-determining 
gene tra-1 III, congenic strains carrying the interval vab-7 - dpy-18 (
markers that flank tra-1) from several different high copy number 
strains have been constructed.  The first of these, using the Bergerac 
strain N62, revealed several polymorphisms mapping between tra-1 and 
dpy-18 (see WBG 8-1: 45).  However, neither of the strains DH424 and 
TR403 appear to contain any extra Tc1 sites in the vab-7 - dpy-18 
interval.  Also, unique probes derived from the two of the N62 
polymorphisms were used to show that the N62 insertion sites are 
vacant in another Bergerac strain, RW7000.  Thus, different high copy 
number strains may have markedly different Tc1 patterns in a given 
Carol Trent reported at the 1985 C.  elegans Meeting that a strain 
carrying Sma-1(e30), derived from N2 by Sydney Brenner, had 
considerably more than thirty copies of Tc1 (the normal N2 number).  
The Cambridge working stock of Sma-1(e30) (designated CB4000) has been 
grown continuously at 15 C for more than fifteen years, by a 
succession of workers at the MRC.  DNA from this stock was compared 
with DNA from the oldest available stock of e30 (designated CB30, 
formerly E30), which has been stored frozen since approximately 1969.  
CB30, which is the ancestor of CB4000, has a Tc1 pattern (EcoRI digest)
identical to N2, but CB4000 has many more copies of Tc1 (more than 
100, i.e.  a smear resembling that seen with DH424 or TR403).  The 
CB4000 strain differs from CB30 in other ways: it grows poorly and has 
a slightly different small phenotype, males are unable to mate, the 
strain is slightly Him, and it has a mutator activity (twitchers and 
other mutants are occasionally segregated).  Therefore it seems that a 
Tc1 mobilization event took place at some point during the maintenance 
of e30 as a 15 C stock, before 1975 but after the original stock, CB30,
had been frozen.  So, who was Prince Charming, and how did he wake up 
Sleeping Beauty?