Worm Breeder's Gazette 9(2): 33

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.

A Polymorphic Foldback Family in C. elegans

D.H. Dreyfus and S.W. Emmons

A restriction fragment polymorphism between two strains of C.  
elegans (Bristol and Bergerac) has been found to be due to the 
insertion into the Bergerac strain of an approximately 1.8 kb DNA 
segment.  The inserted DNA has an inverted repeat structure with no 
separating loop and is visible upon electron microscopic analysis as a 
.85 kb double stranded foldback.  We have named this inserted 
FB1.  FB1 defines a repetitive family of approximately 20 additional 
members visualized by Southern blotting, and about 10 to 20% of the 
sites vary between strains.  The foldback does not cross hybridize 
with TC1, and a preliminary restriction map is not similar to that of 
We have observed that the 1.8 kb foldback structure has 
symmetrically located Hinfl and AluI restriction sites near each end 
of the element.  HinfI cuts nearly at the ends of the element, 
releasing a single internal fragment of 1.77 kb, while AluI cuts 350 
bp internal to the foldback releasing a single 1.1 kb internal 
fragment.  We are currently sequencing several members of this 
polymorphic foldback family as well as the empty site from Bristol 
filled by FB1 in Bergerac.  We hope to determine if this family of 
foldback elements transposes in C.  elegans and if it is similar to 
known foldback transposable elements from other species.
Please let us know about any non-TC1 insertions of approximately 1.8 
kb that we can probe for FB1.  A restriction digest of a potential FB1 
insertion should yield a 1.7 to 1.8 kb Hinfl fragment, and/or a 1.1 kb 
AluI fragment.