Chromosome Numbers in Mammals

Scherthan, Harry

doi:10.1002/9780470015902.a0005799.pub3

Cited by 3 publications

(1 citation statement)

References 43 publications

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“…Chromosome stability in teleost fish is remarkable compared with mammals, where, for example, different deer species have between 3 and 40 haploid chromosomes and different rodents have between 5 and 51 (ref. 29 ). Although the blackfin icefish retains the ancestral chromosome number, many Antarctic notothenioids do not; for example, different species in the genus Notothenia have 13, 12 or 11 chromosomes rather than the ancestral 24 due to centromeric fusions of entire ancestral chromosomes 30 .…”

Section: Genetic Linkage Map and Genome Assembly Integrationmentioning

confidence: 99%

Antarctic blackfin icefish genome reveals adaptations to extreme environments

et al. 2019

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Icefishes (suborder Notothenioidei; family Channichthyidae) are the only vertebrates that lack functional haemoglobin genes and red blood cells. Here, we report a high-quality genome assembly and linkage map for the Antarctic blackfin icefish Chaenocephalus aceratus, highlighting evolved genomic features for its unique physiology. Phylogenomic analysis revealed that Antarctic fish of the teleost suborder Notothenioidei, including icefishes, diverged from the stickleback lineage about 77 million years ago and subsequently evolved cold-adapted phenotypes as the Southern Ocean cooled to sub-zero temperatures. Our results show that genes involved in protection from ice damage, including genes encoding antifreeze glycoprotein and zona pellucida proteins, are highly expanded in the icefish genome. Furthermore, genes that encode enzymes that help to control cellular redox state, including members of the sod3 and nqo1 gene families, are expanded, probably as evolutionary adaptations to the relatively high concentration of oxygen dissolved in cold Antarctic waters. In contrast, some crucial regulators of circadian homeostasis (cry and per genes) are absent from the icefish genome, suggesting compromised control of biological rhythms in the polar light environment. The availability of the icefish genome sequence will accelerate our understanding of adaptation to extreme Antarctic environments.

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Section: Genetic Linkage Map and Genome Assembly Integrationmentioning

confidence: 99%

Antarctic blackfin icefish genome reveals adaptations to extreme environments

et al. 2019

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Chromosome

Klegarth

Eisenberg

2018

The International Encyclopedia of Biological Anthropology

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Chromosomes are condensed, packaged DNA‐containing genes and noncoding regions located in the nucleus of cells and some organelles. Chromosome number and ploidy varies widely between organisms, but mammals typically have haploid gametes and diploid somatic cells. Genetically unique gametes are produced each generation via recombination of chromosomes which occurs predominately during meiosis. Changes in chromosome number and structure within species are often linked to disease phenotypes, whereas nondetrimental changes may delineate species boundaries. Despite sharing a large proportion of our genomes, nonhuman primates and human chromosome structure is highly varied between species. A chromosomal rearrangement separates other great apes from humans by one chromosome pair. Sex‐linked chromosomes (Y‐ and mitochondrial) have been especially integral to the study of human and primate evolution and migration. Studies of chromosomes have rapidly expanded as new sequencing technologies have emerged.

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A RAD-Tag Genetic Map for the Platyfish (Xiphophorus maculatus) Reveals Mechanisms of Karyotype Evolution Among Teleost Fish

et al. 2014

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Mammalian genomes can vary substantially in haploid chromosome number even within a small taxon (e.g., 3-40 among deer alone); in contrast, teleost fish genomes are stable (24-25 in 58% of teleosts), but we do not yet understand the mechanisms that account for differences in karyotype stability. Among perciform teleosts, platyfish (Xiphophorus maculatus) and medaka (Oryzias latipes) both have 24 chromosome pairs, but threespine stickleback (Gasterosteus aculeatus) and green pufferfish (Tetraodon nigroviridis) have just 21 pairs. To understand the evolution of teleost genomes, we made a platyfish meiotic map containing 16,114 mapped markers scored on 267 backcross fish. We tiled genomic contigs along the map to create chromosome-length genome assemblies. Genome-wide comparisons of conserved synteny showed that platyfish and medaka karyotypes remained remarkably similar with few interchromosomal translocations but with numerous intrachromosomal rearrangements (transpositions and inversions) since their lineages diverged 120 million years ago. Comparative genomics with platyfish shows how reduced chromosome numbers in stickleback and green pufferfish arose by fusion of pairs of ancestral chromosomes after their lineages diverged from platyfish 195 million years ago. Zebrafish and human genomes provide outgroups to root observed changes. These studies identify likely genome assembly errors, characterize chromosome fusion events, distinguish lineage-independent chromosome fusions, show that the teleost genome duplication does not appear to have accelerated the rate of translocations, and reveal the stability of syntenies and gene orders in teleost chromosomes over hundreds of millions of years.

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Chromosome Numbers in Mammals

Cited by 3 publications

References 43 publications

Antarctic blackfin icefish genome reveals adaptations to extreme environments

Antarctic blackfin icefish genome reveals adaptations to extreme environments

Chromosome

A RAD-Tag Genetic Map for the Platyfish (Xiphophorus maculatus) Reveals Mechanisms of Karyotype Evolution Among Teleost Fish

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