Karyotypic fissioning and Canid phylogeny

Todd, Neil B.

doi:10.1016/0022-5193(70)90096-2

Cited by 87 publications

(51 citation statements)

References 28 publications

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“…This comes as no surprise, because vast information hidden on the genome level is still to be explored to put the evolution jig-saw puzzle together (Eppig 1996). Todd (1970) suggested that the ancestral karyotype consisted of 14 chromosomes, whereas Matthey (1973) considered a chromosome number of 2n = 48 ‫ע‬ 8 as the ancestral eutherian condition. Still others favored an intermediate chromosome number like that of the cat (Rettenberger et al 1995b).…”

Section: Discussionmentioning

confidence: 99%

Emerging Patterns of Comparative Genome Organization in Some Mammalian Species as Revealed by Zoo-FISH

Chowdhary¹,

Raudsepp²,

Frönicke³

et al. 1998

Genome Res.

212

143

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Although gene maps for a variety of evolutionarily diverged mammalian species have expanded rapidly during the past few years, until recently it has been difficult to precisely define chromosomal segments that are homologous between species. A solution to this problem has come from the development of Zoo-FISH, also known as cross-species chromosome painting. The use of Zoo-FISH to identify regions of chromosomal homology has allowed the transfer of information from map-rich species such as human and mouse to a wide variety of other species. From a Zoo-FISH analysis spanning four mammalian orders (Primates, Artiodactyla, Carnivora, and Perissodactyla), and involving eight species (human, pig, cattle, Indian muntjac, cat, American mink, harbor seal, and horse), three distinct classes of synteny conservation have been designated: (1) conservation of whole chromosome synteny, (2) conservation of large chromosomal blocks, and (3) conservation of neighboring segment combinations. This analysis has also made it possible to identify a set of chromosome segments (based on human chromosome equivalents) that probably made up the karyotype of the common ancestor of the four orders. This approach provides a basis for developing a picture of the ancestral mammalian karyotype, but a full understanding will depend on studies encompassing more diverse combinations of mammalian orders.

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Section: Discussionmentioning

confidence: 99%

Emerging Patterns of Comparative Genome Organization in Some Mammalian Species as Revealed by Zoo-FISH

Chowdhary¹,

Raudsepp²,

Frönicke³

et al. 1998

Genome Res.

212

143

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“…aryotypic fission theory explains diverse mammalian karyotypes in taxa that include Canidae (2n ϭ 34-78), Artiodactyla (2n ϭ 14-74), Old World monkeys and apes (2n ϭ 42-72), and lemurs (2n ϭ 20-70) (1)(2)(3)(4). The ancestral chromosomal complement for all mammals, in theory, was comprised of large mediocentric (i.e., metacentric, submetacentric, and subtelocentric) chromosomes (2n ϭ 14), from which episodes of chromosome fission generated karyotypes with higher diploid numbers and smaller chromosomes (5).…”

mentioning

confidence: 99%

“…The ancestral chromosomal complement for all mammals, in theory, was comprised of large mediocentric (i.e., metacentric, submetacentric, and subtelocentric) chromosomes (2n ϭ 14), from which episodes of chromosome fission generated karyotypes with higher diploid numbers and smaller chromosomes (5). In populations with all mediocentric autosomes, a karyotypic fission event introduces a full complement of homologous acrocentric derivatives (1). Varying retention of ancestral mediocentric linkages and incorporation of fission-generated acrocentric pairs potentially generates a diploid range with up to twice the ancestral number of autosomes.…”

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confidence: 99%

Kinetochore reproduction in animal evolution: Cell biological explanation of karyotypic fission theory

Kolnicki

2000

Proc. Natl. Acad. Sci. U.S.A.

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Karyotypic fission theory of Todd offers an explanation for the diverse range of diploid numbers of many mammalian taxa. Theoretically, a full complement of acrocentric chromosomes can be introduced into a population by chromosomal fission. Subsequent inheritance of ancestral chromosomes and paired fission derivatives potentially generates a diploid range from the ancestral condition to double its number of chromosomes. Although it is undisputed that both chromosomal fission and fusion (''Robertsonian rearrangements'') have significantly contributed to karyological diversity, it is generally assumed that independent events, the fission of single chromosomes or the fusion of two chromosomes, are the sources of such change. The karyotypic fission idea by contrast posits that all mediocentric chromosomes simultaneously fission. Here I propose a specific cell biological mechanism for Todd's karyotypic fission concept, ''kinetochore reproduction theory,'' where a complete set of dicentric chromatids is synthesized during gametogenesis, and kinetochore protein dephosphorylation regulates dicentric chromatid segregation. Three postulates of kinetochore reproduction theory are: (i) breakage of dicentric chromosomes between centromere pairs forms acrocentric derivatives, (ii) de novo capping of newly synthesized acrocentric ends with telomeric DNA stabilizes these derivatives, and (iii) mitotic checkpoints regulate chromosomal disjunction to generate fissioned karyotypes. Subsequent chromosomal rearrangement, especially pericentric inversion, increases the probability of genetic isolation amongst incipient sympatric species polytypic for fissiongenerated acrocentric autosomes. This mechanism obviates the requirement for numerous independent Robertsonian rearrangements and neatly accounts for mammalian karyotype evolution as exemplified in analyses of Carnivora, Artiodactyla, and Primates.

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“…Thus Todd's (1970) recent sugges tion of a basic diploid count of 38 for pedigreed stock does not seem to be well founded. While a modal number of 38 has been established by some investigators, the results of this study and others makes it quite apparent that this number may vary, for both domesticated and wild foxes, not only in different individuals, but also between cells of different tissues from the Cytologia 37 same animal.…”

Section: Resultsmentioning

confidence: 99%