"Compartments and polyclones in insect development"

Date:
1973-1975
Reference:
PP/CRI/H/5/11
Catalogue details

Licence: In copyright

Credit: "Compartments and polyclones in insect development". Source: Wellcome Collection.

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    ór >• j t UwOL ,. ( <- C£AéL__ ckoloAv^ CVdU) . i —_ - 5 - U&A-3 ^ a, Sxt-p^c . \ do not neatly cover the entire epithelial surface without either overlapping or leaving spaces. On the contrary, if two patches from separate individuals have ended up in roughly the same place then it is (ilmosj: always found that they each partly overlap Cvt(A t^»uGAÄ<2. the other. This result shows that the development of Drosophila epithelium is not l&vfLOÄ.-.--<« strictly clonal , even after the blastoderm stage. (It has been known for a long time that the overall development of Drosophila was not clonal but this is not too surpris- / ing when one considers how the blastoderm is formed; see Benzer ' ). If it were strictly clonal the developmental history of the same cell (say, a particular / bristle cell) in different individuals would always be exactly the same. These results > ^ show clearly that even after the blastoderm the total lineage of a particular epithelial y cell in Drosophila is not invariant. ' After all these preliminaries we can now approach the important result. Let us assume that our hypothetical piece of epithelium is roughly smooth in outline, as shown in Fig. Then perhaps it is not too surprising to learn that a black patch near the borders of our special piece of epithelium has itself a rather smooth outline where it follows the boundary of the area but has a rough outline elsewhere. However we will not linger over this because a similar but more striking result is to follow. We assume that at the earliest stage of marking (that is, when the disc is first formed) a black patch can occur anywhere within our area. In particular it may have the size and shape shown in Fig. We now ask: suppose the mark is made a little later, say, one cell generation later, what will a patch be like? Naturally it will, on an average, be half the size and we expect it to have an surprising restriction appears. When all the results from many different patches are combined it is found that a rather smooth line (marked XY) can be drawn, dividing our hypothetical area with distinct parts, such that no black patch, made at this later time , will ever cross this line. Moreover the outline of a patch touching PTO