Gene activity in early development / Eric H. Davidson.

  • Davidson, Eric H., 1937-2015.
Date:
[1968], ©1968
Catalogue details

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

Credit: Gene activity in early development / Eric H. Davidson. Source: Wellcome Collection.

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    18 I. GENE ACTIVITY IN EARLY EMBRYOGENESIS Studied by Boveri and his followers resulted in the early death of the hybrids; it has been shown that in many cases the early arrest and death of hybrids is associated with mitotic failures and the elimination of a significant portion of the chromosomes. This phenomenon was first established by Boveri's stu¬ dent Baltzer, in 1910, in a study of hybrids formed by fertilizing Sfherechi- nus eggs with Strongylocentrotus (Parecentrotus) sperm (39). These hybrids rarely survive up to the pluteus stage, and when they do they display ma¬ ternal, rather than hybrid skeletal, characteristics. Baltzer showed that these results are due to the elimination of most of the paternal chromosomes in the course of the cleavage mitoses. Early arrest, lethality, and failure of true diploid hybrid formation stemming from similar mitotic irregularities Mesenchyme blastula Early gastrula Midgastrula Late gastrula 13 hr 20 hr 22 hr 24 hr 21 hr 23 hr 24 hr 29 hr 16 hr 24 hr 25 hr 45 hr Figure 5. Development of hybrid and parental sea urchin embryos. (PP) Parental type Paracentrotus Uvidus ( $ ); (AA) parental type Arbacta Uxula ( ^O; (PA) hybrid intermixture of parental types. Note primary mesenchyme cells ap¬ pearing in blastulae, secondary mesenchyme, and invagination in gastrulae, with skeletal rod formation ensuing. Hybrid embryos may progress as far as skeletal rod formation (PA, 45 hr), but development beyond mesenchyme blastula stage (PA, 16 hr) is retarded. Hybrid mesenchyme blastula is of thin-walled, maternal form (PP, 13 hr). Whiteley, A. H., and Baltzer, F., Puhhl. Staz. Zool. Napoli 30, 402 (1958).