Worm Breeder's Gazette 7(2): 34

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.

Arrangement of Tc1 in New C. elegans Strains

D. Katzenberg, S. Emmons

Figure 1

We have isolated DNA from most of the new wild isolates of C.  
elegans described elsewhere in this issue by Dick Russell and 
coworkers and analyzed the pattern of bands produced when a cloned 
copy of the transposon Tc1 is hybridized to a restriction digest on a 
Southern.  From the fractionated restriction digests we have found 
that all these strains have a ribosomal repeat length identical to 
Bristol.  The hybridization with Tc1 gave two interesting findings.  
One is that all the wild strains have a series of bands similar in 
number to Bristol and clearly different from the smear in Bergerac.  
Thus Bergerac may be an unusual case and represent aberrant regulation 
of the transposon.
The second finding is that some differences in the pattern of bands 
are seen among these strains.  The same result was reported earlier by 
Rosenzweig, Liao and Hirsh, Newsletter Vol. 7, no. 1, p.51.  We assume 
without direct evidence that these differences are due to 
transposition of Tc1 because we know that transpositions have occurred 
more frequently than point mutations during the divergence of Bristol 
and Bergerac.  Our Southerns so far visualize as bands a minority of 
the hybridizing material, most of which remains in large, 
unfractionated fragments at the top of the gel, and therefore our 
analysis must be considered preliminary.  Nevertheless, based on the 
fragments we do see, we find the strains falling into the following 
categories (with the number of bands differing relative to Bristol (N2)
shown in parentheses)
[See Figure 1]
It seems very surprising on the one hand that worms isolated in 
California in the 1970's should be so similar to a worm isolated in 
England in the 1940's, and on the other hand that worms isolated from 
a single garden (the Ga series) should differ as much from each other 
as they do from the older English isolate.  The first fact might 
reflect a greater degree of world-wide mixing of worms (wind, water, 
birds' feet?) than we had naively supposed.  The second might result 
from reproduction by selfing, which suppresses genetic exchange within 
a population.

Figure 1