Mammalian chimaeras / Anne McLaren.

  • McLaren, Anne.
Date:
[1976]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Mammalian chimaeras / Anne McLaren. Source: Wellcome Collection.

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    68 Other morphological characters Fig. 24. The xiphisterna of nineteen chimaeras arranged in ascending order of abnormality. In the first row, one normal and six with a varying degree of involve¬ ment of the xiphoid cartilage (white) and its calcified granules (stippled); the second row has mild and the third more marked involvement of the osseous xiphisternum (black). From Grüneberg & McLaren (1972). anomalies produced by short ear and vestigial tail in different parts of the body. If the genes act locally, this correlation suggests that the two chimaera components were distributed fairly evenly in the skeletal primordia. With respect to bifurcation of the xiphisternum, 18/19 chimaeras showed abnormalities, compared with only 28/70 se¡+ heterozygotes. The degree of abnormality was also greater in the chimaeras, encompassing the whole spec¬ trum of manifestation except for the extreme homozygous condition (Fig. 24). The ulnar sesamoid bone in the foot is either absent or very much reduced in se/se animals. The size of the bone shows a high degree of symmetry be¬ tween right and left sides in +/+ and sel+ animals. In chimaeras (Fig. 25), the right-left symmetry is less marked, and varying degrees of intermediate expression are seen. The asymmetry suggests that bone size is determined locally, by the cell populations present in the bone rudiment, rather than by a systemic (e.g. hormonal) effect determined elsewhere in the body. The fact that some correlation between sides remains is probably due to variations in