(b, 3) (5,4) , using which one substitutes the substring (b,2)(4,5)(3,2) by the substring (b, 3)(5, 4).
During macronuclear development the lESs are excised and the MDSs are ligated (by overlapping of the ends) to yield a macronuclear gene. MDSs are rectangles. lESs are line segments between rectangles. 30 2 Ciliates MDSs. lESs are usually less than 100 nucleotides long, and they may occur at any position in a gene. Extrapolation from the structure of 12 micronuclear genes known in one stichotrich indicates that more than 100,000 lESs are present in all the genes in a haploid genome. The significance of these bizarre lESs is not known.
7. Fig. 7. The overlap graph that is obtained from many different legal strings, where the pointers P2, P3, P4, and P6 are negative, and pointers P5 and P7 are positive. In the following chapters we shall study in detail the models of MDS descriptors, legals strings, and overlap graphs. We study them in this order, and hence in the increasing order of abstraction. 3 Formalizing Molecular Operations Whichever model we choose for representing gene structures, we also have to represent the molecular operations from Chap.