. Il bollettino biologico. Biologia; Zoologia; biologia; biologia marina. Genetica riproduttiva del Pacifico TRIPLOID OSTRICHE 315. Numero di cromosomi figura 3. Distnhution del numero di cromosomi per cellula in 2-4 cellula diploide (femmina) > tnploid (DT) e tnploid (femmina) x embrioni diploide (TD) della Pacific oyster, mostrando alcuni TD embrioni aveva alti numeri di cromosoma dove DT non ha. I risultati di questo studio suggeriscono che non vi sono differenze importanti tra la meiosi in tnploid maschi e femmine. Primo, il cromosoma numeri in embrioni di DT sono più vicini alla distribuzione teorica di quelle in TD ricama

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. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. REPRODUCTIVE GENETICS OF TRIPLOID PACIFIC OYSTERS 315. Chromosome Number Figure 3. Distnhution of number of chromosomes per cell in 2-4 cell diploid (female) > tnploid (DT) and tnploid (female) x diploid embryos (TD) of the Pacific oyster, showing some TD embryos had high chromosome numbers where DT did not. Results of this study suggest that there are important differences between meiosis in tnploid males and females. First, chromosome numbers in DT embryos are closer to the theoretical distribution than those in TD embryos, and TD embryos had more cells with 25+ chromosomes than DT embryos. Second, survivors from TD crosses were primarily polyploid, and survivors in DT crosses were primarily diploids. These observations suggest that meiosis in triploid females is more likely to make mistakes and produce gametes with chromosome gains rather than losses, compared with meiosis in triploid males. We hy- pothesize that in eggs from triploids, there is a general mechanism of pro-egg segregation which favors the re- tention, rather than loss, of chromosomes by the egg pro- nucleus. In eggs, meiotic divisions are characterized by the for- mation of two polar bodies. We propose that segregation errors occur more often in the egg than in sperm; and when those errors occur, the egg tends to retain the errant chromosome(s) (either univalents or nondisjoined biva- lents) rather than rejecting them into the polar body. In contrast, meiotic divisions in males produce four sperm, and therefore missegregated chromosomes are randomly distributed into daughter cells by default. The suppression of meiosis I and the formation of diploid gametes can be considered extreme cases of pro-egg segregation, which rarely occur in males. Pro-egg segregation would have a selective advantage because the gain of chromosomes is generally less harmful than their loss. Overall, the pro-egg segregation hypothesis predicts that me

Parole chiave associate all'immagine

• bookauthorlilliefrankrat
• booksubjectbiology
• booksubjectzoology