. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 312 X. GUO AND S. K. ALLEN, Figure 1. Synapsis and meiosis in eggs from triploid Pacific oysters: A—metaphase I eggs from diploids with 10 bivalents; B—complete synapsis in metaphase I eggs from triploids with 10 trivalents; C—incomplete synapsis in metaphase I eggs from triploids with a mixture of uni-, bi-, and trivalents; D—metaphase 11 in eggs from triploids; E—anaphase II in eggs from triploids; and F—metaphase of the first mitotic division of an embryo from a tnploid (female) x diploid cross. The orcein staining p
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 312 X. GUO AND S. K. ALLEN, Figure 1. Synapsis and meiosis in eggs from triploid Pacific oysters: A—metaphase I eggs from diploids with 10 bivalents; B—complete synapsis in metaphase I eggs from triploids with 10 trivalents; C—incomplete synapsis in metaphase I eggs from triploids with a mixture of uni-, bi-, and trivalents; D—metaphase 11 in eggs from triploids; E—anaphase II in eggs from triploids; and F—metaphase of the first mitotic division of an embryo from a tnploid (female) x diploid cross. The orcein staining protocol used in this study was highly reliable for determining chromosome numbers in early embryos. Often more than half of the embryos had meta- phases that could be clearly counted, and it was not un- usual for embryos to have two countable metaphases. Most importantly, there is no artifactual chromosome loss. In the DD crosses, 49 of the 50 embryos analyzed had 20 chromosomes, and one had 30 chromosomes (Table V). In other crosses, the average chromosome numbers were for DT, for TD, and for TT. TD embryos had a slightly greater mean chromosome number and coefficient of variation than DT crosses. The distribution of chromosome numbers among embryos in DT and TD crosses is shown in Figure 3. Comparatively, the distri- bution of chromosome numbers of DT embryos was closer to that expected from the random segregation of the third chromosome set than was the distribution of chromosome numbers in TD embryos. The latter had more embryos with 25+ chromosomes than DT crosses. Flow cytometric analysis of 24-hour-old embryos showed the same pattern, and the mean ploidy levels were c for DT, c for TD, and c for TT crosses (Table III). Mean coefficient of variation ofDNA content among the four groups was highest in the TD cross (Table III). Over time, the aneuploid peak in TD crosses split into two peaks: one close to 2 n and the other close to 3
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
