Conservation of chromosome 1 in turtles over 66 million years

Mühlmann-Díaz, María C.; Ulsh, Brant A.; Whicker, F.W.; Hinton, Thomas G.; Congdon, Justin D.; Robinson, Jeannie; Bedford, Joel S.

doi:10.1159/000056885

Cited by 13 publications

(7 citation statements)

References 36 publications

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“…Vice versa, deletions limiting the accumulation of functionally dispensable DNAs would be more frequent in squamates (Olmo et al, 2002). Similar differences in evolutionary rate are also noted in chromosome morphology, which is much more conservative in chelonians (Bickham, 1981;Olmo, 1986;Muhlmann-Diaz et al, 2001) and in coding sequences, which in squamates evolved at a faster rate than in turtles, crocodiles and birds (Hughes and Mouchiroud, 2001). These data could be explained by the model proposed by Hartl and Petrov (Hartl, 2000;Petrov et al, 2000;Petrov, 2001Petrov, , 2002.…”

Section: Discussionsupporting

confidence: 55%

Reptiles: a group of transition in the evolution of genome size and of the nucleotypic effect

Olmo¹

2003

Cytogenet Genome Res

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A comparison between genome size and some phenotypic parameters, such as developmental length and metabolic rate, showed in reptiles a nucleotypic correlation similar to the one observed in birds and mammals. Indeed, like homeotherms, reptiles exhibit a highly significant, inverse correlation of genome size with metabolic rate but unlike amphibians, no relationship with developmental length. Several lines of evidence suggest that these nucleotypic correlations are influenced by body temperature, which also affects the guanine + cytosine nuclear percentage, and that they play an important role in the adaptation of these amniotes. However, the reptilian suborders exhibit differences in the quantitative and compositional characters of the genome that do not completely correspond to differences in the phenotypic parameters commonly involved in the nucleotypic effect. Thus, additional factors could have influenced genome size in this class. These data could be explained with the model of Hartl and Petrov, who observed an inverse correlation between genome size, non-coding portion of the genome and rate of DNA loss and hypothesized a strong role for different spectra of spontaneous insertions and deletions (indels) in the variations of genome size. It is thus reasonable to surmise that variations in the reptilian genome were initially influenced by different indels spectra typical of the diverse lineages, possibly related to different chromosome compartmentalizations. The consequent size increases or decreases would have influenced various morphological and functional cell parameters, and through these some phenotypic characteristics of the whole organism, especially the metabolic rate, very important for environmental adaptation and thus subject to natural selection. Through this “nucleotypic” bond, natural selection would also have controlled genome size variations.

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Section: Discussionsupporting

confidence: 55%

Reptiles: a group of transition in the evolution of genome size and of the nucleotypic effect

Olmo¹

2003

Cytogenet Genome Res

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“…This variation in the Gbanding pattern in Pleurodiran turtles establishes a different karyotypic evolution from that identified for the suborder Cryptodira. Previous reports have suggested genomic stability in Cryptodiran turtles, in which both the banded chromosome morphology (Bickham, 1981) and the DNA sequences inside the chromosomes (Muhlmann-Díaz et al, 2001) remain unchanged for millions of years.…”

Section: Resultsmentioning

confidence: 99%

Karyotypic characterization of Hydromedusa tectifera (Testudines, Pleurodira) from the upper Iguaçu River in the Brazilian state of Paraná

et al. 2006

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We present the karyotypic characterization of 26 specimens of the side-necked turtle Hydromedusa tectifera collected in the upper Iguaçu River, Paraná state, Brazil. The turtles were cytogenetically analyzed using Giemsa staining and other banding techniques (C, G, Ag-NOR and CMA 3 ) as well as fluorescence in situ hybridization (FISH) with a rDNA 18S probe. All the specimens showed a diploid number of 58 composed of 22 macro and 36 microchromosomes. The Ag-NOR, CMA 3 and FISH techniques permitted the identification and characterization of the chromosome pairs bearing nucleolus organizer regions (NORs), while G-banding facilitated a better recognition and pairing of macrochromosomes. These data agree with some information available in the literature and should be very useful for further cytotaxonomic and cytosystematic studies.

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“…For some reptiles and primitive amphibians the presence of microchromosomes would suggest few intra-and interchromosomal rearrangements reached fixation. This is supported by the conservative nature of many reptilian and primitive amphibian karyotypes (Morescalchi et al, 1977a(Morescalchi et al, , 1977b(Morescalchi et al, , 1979Mühlmann-Diaz, 2001). …”

Section: A "Fission-fusion Model" Of Microchromosome Evolutionmentioning

confidence: 96%

Origin and evolution of avian microchromosomes

Burt¹

2002

Cytogenet Genome Res

225

262

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The origin of avian microchromosomes has long been the subject of much speculation and debate. Microchromosomes are a universal characteristic of all avian species and many reptilian karyotypes. The typical avian karyotype contains about 40 pairs of chromosomes and usually 30 pairs of small to tiny microchromosomes. This characteristic karyotype probably evolved 100–250 million years ago. Once the microchromosomes were thought to be a non-essential component of the avian genome. Recent work has shown that even though these chromosomes represent only 25% of the genome; they encode 50% of the genes. Contrary to popular belief, microchromosomes are present in a wide range of vertebrate classes, spanning 400–450 million years of evolutionary history. In this paper, comparative gene mapping between the genomes of chicken, human, mouse and zebrafish, has been used to investigate the origin and evolution of avian microchromosomes during this period. This analysis reveals evidence for four ancient syntenies conserved in fish, birds and mammals for over 400 million years. More than half, if not all, microchromosomes may represent ancestral syntenies and at least ten avian microchromosomes are the product of chromosome fission. Birds have one of the smallest genomes of any terrestrial vertebrate. This is likely to be the product of an evolutionary process that minimizes the DNA content (mostly through the number of repeats) and maximizes the recombination rate of microchromosomes. Through this process the properties (GC content, DNA and repeat content, gene density and recombination rate) of microchromosomes and macrochromosomes have diverged to create distinct chromosome types. An ancestral genome for birds likely had a small genome, low in repeats and a karyotype with microchromosomes. A “Fission–Fusion Model” of microchromosome evolution based on chromosome rearrangement and minimization of repeat content is discussed.

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Conservation of chromosome 1 in turtles over 66 million years

Cited by 13 publications

References 36 publications

Reptiles: a group of transition in the evolution of genome size and of the nucleotypic effect

Reptiles: a group of transition in the evolution of genome size and of the nucleotypic effect

Karyotypic characterization of Hydromedusa tectifera (Testudines, Pleurodira) from the upper Iguaçu River in the Brazilian state of Paraná

Origin and evolution of avian microchromosomes

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