Chromosomal evolution within the family Estrildidae (Aves) I. The Poephilae

Christidis, Leslie

doi:10.1007/bf00058691

Cited by 35 publications

(31 citation statements)

References 45 publications

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“…Polymorphisms of this type have been described in mammals (e.g. Davis et al 1986;Hale 1986), birds (Ansari and Kaul 1979;Christidis 1986), reptiles (Moritz 1984) and some fish species (e.g. Vitturi et al 1984Vitturi et al , 1993bTurner et al 1985).…”

Section: Discussionmentioning

confidence: 97%

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

et al. 1996

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A consistent diploid number of 2n = 36 was determined for the sea urchin Paracentrotus lividus from the Gulf of Palermo by analysis of mitotic chromosomes of both early developing embryos and male gonads. The haploid number n = 18 was determined by counts of spermatocyte bivalents at diakinesis. A heteromorphic chromosome sex mechanism of the XY type is likely present in this species. This is indicated by the occurrence of a chromosomal pair, pair No. 2, which is heteromorphic in both morphology and size in about 50% of the mitotic figures (metaphases and anaphases) of embryos. In addition, heteromorphism of the same pair of chromosomes occurred during spermatogonial metaphases in the five male specimens investigated here. The detection of a low chromosome number (2n--36) compared to other echinoids (2n = 42 to 44), a heteromorphic chromosome sex system and the involvement of three chromosome pairs in nucleolar organization (NORs) provide evidence of the specialization of the P. lividus karyotype.

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Section: Discussionmentioning

confidence: 97%

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

et al. 1996

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“…In fact, several reports of within-species variation in sex chromosome morphology provide evidence for an on-going process of sex chromosome evolution. Specifically, different forms (varying in size and centromere position) of W were found in wheatears [27] and in grassfinches [25].…”

Section: Discussionmentioning

confidence: 99%

The long and the short of avian W chromosomes: no evidence for gradual W shortening

2012

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The well-established view of the evolution of sex chromosome dimorphism is of a gradual genetic and morphological degeneration of the hemizygous chromosome. Yet, no large-scale comparative analysis exists to support this view. Here, we analysed karyotypes of 200 bird species to test whether the supposed directional changes occur in bird sex chromosomes. We found no support for the view that W chromosomes gradually become smaller over evolutionary time. On the contrary, the length of the W chromosome can fluctuate over short time scales, probably involving both shortening and elongation of non-coding regions. Recent discoveries of near-identical palindromes and neo-sex chromosomes in birds may also contribute to the observed variation. Further studies are now needed to investigate how chromosome morphology relates to its gene content, and whether the changes in size were driven by selection.

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“…Among mammals, the creeping vole Microtus oregoni has XY somatic cells and Y0 germ cells in male and X0 somatic cells and XX germ cells in females (Ohno 1967); and some marsupial species eliminate one X chromosome in females and the Y chromosome in males from selected somatic tissues (Hayman and Martin 1974). In the zebra finch, the absence of the GRC has been so far demonstrated in several somatic tissues, such as bone marrow (Takagi 1972;Pigozzi and Solari 1998;Christidis 1986), liver, and muscle (Itoh and Arnold 2005), both in male and female individuals. These evidences strongly suggest that the GRC is restricted to the germ cells at the moment of their differentiation in early embryogenesis.…”

Section: Possible Mechanisms Of Transmission and Restriction To The Gmentioning

confidence: 98%

The germ-line-restricted chromosome in the zebra finch: recombination in females and elimination in males

2005

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In the zebra finch (Taeniopygia guttata), there is a germ-line-restricted chromosome regularly present in males and females. A reexamination of male and female meiosis in the zebra finch showed that this element forms a euchromatic bivalent in oocytes, but it is always a single, heterochromatic element in spermatocytes. Immunostaining with anti-MLH1 showed that the bivalent in oocytes has two or three foci with a localized pattern, indicating the regular occurrence of recombination. In male meiosis, the single restricted chromosome forms an axis that contains the cohesin subunit SMC3, and the associated chromatin is densely packed until late pachytene. Electron microscopy of thin-sectioned seminiferous tubules shows that the restricted chromosome is eliminated in postmeiotic stages in the form of packed chromatin inside a micronucleus, visible in the cytoplasm of young spermatids. The selective condensation of the restricted chromosome during early meiotic prophase in males is interpreted as a strategy to avoid the triggering of asynaptic checkpoints, but this condensation is reversed prior to the final condensation that leads to its (ulterior) elimination. Recombination during female meiosis may prevent the genetic attrition of the restricted chromosome and, along with the elimination in male germ cells, ensures its regular transmission through females.

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Chromosomal evolution within the family Estrildidae (Aves) I. The Poephilae

Cited by 35 publications

References 45 publications

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

The long and the short of avian W chromosomes: no evidence for gradual W shortening

The germ-line-restricted chromosome in the zebra finch: recombination in females and elimination in males

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