Repetitive sequences form a substantial and still enigmatic part of the mammalian genome. We isolated repetitive DNA blocks of the X chromosomes of three species of the family Bovidae: Kobus defassa (KDEXr sequence), Bos taurus (BTAXr sequence) and Antilope cervicapra (ACEXr sequence). The copy numbers of the isolated sequences were assessed using qPCR, and their chromosomal localisations were analysed using FISH in ten bovid tribes and in outgroup species. Besides their localisation on the X chromosome, their presence was also revealed on the Y chromosome and autosomes in several species. The KDEXr sequence abundant in most Bovidae species also occurs in distant taxa (Perissodactyla and Carnivora) and seems to be evolutionarily older than BTAXr and ACEXr. The ACEXr sequence, visible only in several Antilopini species using FISH, is probably the youngest, and arised in an ancestor common to Bovidae and Cervidae. All three repetitive sequences analysed in this study are interspersed among gene-rich regions on the X chromosomes, apparently preventing the crossing-over in their close vicinity. This study demonstrates that repetitive sequences on the X chromosomes have undergone a fast evolution, and their variation among related species can be beneficial for evolutionary studies.

• Klíčová slova
• Bovidae, FISH, X chromosome, laser microdissection, qPCR, repetitive sequence, sequence analysis,
• MeSH
• antilopy * genetika   MeSH
• chromozom Y genetika   MeSH
• DNA MeSH
• lidé MeSH
• lidské chromozomy X MeSH
• repetitivní sekvence nukleových kyselin genetika   MeSH
• skot genetika   MeSH
• vysoká zvěř * genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• skot genetika   MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA MeSH

We identified a small, supernumerary marker chromosome (sSMC) in two phenotypically normal Asian elephants (Elephas maximus): a female (2n = 57,XX,+mar) and her male offspring (2n = 57,XY,+mar). sSMCs are defined as structurally abnormal chromosomes that cannot be identified by conventional banding analysis since they are usually small and often lack distinct banding patterns. Although current molecular techniques can reveal their origin, the mechanism of their formation is not yet fully understood. We determined the origin of the marker using a suite of conventional and molecular cytogenetic approaches that included (a) G- and C-banding, (b) AgNOR staining, (c) preparation of a DNA clone using laser microdissection of the marker chromosome, (d) FISH with commercially available human painting and telomeric probes, and (e) FISH with centromeric DNA derived from the centromeric regions of a marker-free Asian elephant. Moreover, we present new information on the location and number of NORs in Asian and savanna elephants. We show that the metacentric marker was composed of heterochromatin with NORs at the terminal ends, originating most likely from the heterochromatic region of chromosome 27. In this context, we discuss the possible mechanism of marker formation. We also discuss the similarities between sSMCs and B chromosomes and whether the marker chromosome presented here could evolve into a B chromosome in the future.

• Klíčová slova
• Asian elephant, FISH, NOR, heterochromatin, karyotype, laser microdissection, sSMC, savanna elephant, small supernumerary marker chromosome,
• Publikační typ
• časopisecké články MeSH

Chromosome structural change has long been considered important in the evolution of post-zygotic reproductive isolation. The premise that karyotypic variation can serve as a possible barrier to gene flow is founded on the expectation that heterozygotes for structurally distinct chromosomal forms would be partially sterile (negatively heterotic) or show reduced recombination. We report the outcome of a detailed comparative molecular cytogenetic study of three antelope species, genus Raphicerus, that have undergone a rapid radiation. The species are largely conserved with respect to their euchromatic regions but the X chromosomes, in marked contrast, show distinct patterns of heterochromatic amplification and localization of repeats that have occurred independently in each lineage. We argue a novel hypothesis that postulates that the expansion of heterochromatic blocks in the homogametic sex can, with certain conditions, contribute to post-zygotic isolation. i.e., female hybrid incompatibility, the converse of Haldane's rule. This is based on the expectation that hybrids incur a selective disadvantage due to impaired meiosis resulting from the meiotic checkpoint network's surveillance of the asymmetric expansions of heterochromatic blocks in the homogametic sex. Asynapsis of these heterochromatic regions would result in meiotic silencing of unsynapsed chromatin and, if this persists, germline apoptosis and female infertility.

• MeSH
• antilopy klasifikace   genetika   MeSH
• chromozom X ultrastruktura   MeSH
• heterozygot MeSH
• hybridizace genetická MeSH
• hybridizace in situ fluorescenční MeSH
• karyotyp * MeSH
• meióza MeSH
• modely genetické * MeSH
• rekombinace genetická MeSH
• reprodukční izolace * MeSH
• sexuální faktory MeSH
• tok genů MeSH
• vznik druhů (genetika) * MeSH
• ženská infertilita genetika   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Afrika MeSH

The taxonomy and phylogenetics of Neotropical deer have been mostly based on morphological criteria and needs a critical revision on the basis of new molecular and cytogenetic markers. In this study, we used the variation in the sequence, copy number, and chromosome localization of satellite I-IV DNA to evaluate evolutionary relationships among eight Neotropical deer species. Using FISH with satI-IV probes derived from Mazama gouazoubira, we proved the presence of satellite DNA blocks in peri/centromeric regions of all analyzed deer. Satellite DNA was also detected in the interstitial chromosome regions of species of the genus Mazama with highly reduced chromosome numbers. In contrast to Blastocerus dichotomus, Ozotoceros bezoarticus, and Odocoileus virginianus, Mazama species showed high abundance of satIV DNA by FISH. The phylogenetic analysis of the satellite DNA showed close relationships between O. bezoarticus and B. dichotomus. Furthermore, the Neotropical and Nearctic populations of O. virginianus formed a single clade. However, the satellite DNA phylogeny did not allow resolving the relationships within the genus Mazama. The high abundance of the satellite DNA in centromeres probably contributes to the formation of chromosomal rearrangements, thus leading to a fast and ongoing speciation in this genus, which has not yet been reflected in the satellite DNA sequence diversification.

• Klíčová slova
• Cervidae, FISH, comparative cytogenetics, satellite DNA, sequencing,
• MeSH
• fibroblasty MeSH
• fylogeneze * MeSH
• genetické markery MeSH
• hybridizace in situ fluorescenční MeSH
• kultivované buňky MeSH
• kůže cytologie   MeSH
• primární buněčná kultura MeSH
• satelitní DNA genetika   MeSH
• vysoká zvěř klasifikace   genetika   MeSH
• vznik druhů (genetika) MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• genetické markery MeSH
• satelitní DNA MeSH

Centromeric and pericentromeric chromosome regions are occupied by satellite DNA. Satellite DNAs play essential roles in chromosome segregation, and, thanks to their extensive sequence variability, to some extent, they can also be used as phylogenetic markers. In this paper, we isolated and sequenced satellite DNA I-IV in 11 species of Cervidae. The obtained satellite DNA sequences and their chromosomal distribution were compared among the analysed representatives of cervid subfamilies Cervinae and Capreolinae. Only satI and satII sequences are probably present in all analysed species with high abundance. On the other hand, fluorescence in situ hybridisation (FISH) with satIII and satIV probes showed signals only in a part of the analysed species, indicating interspecies copy number variations. Several indices, including FISH patterns, the high guanine and cytosine (GC) content, and the presence of centromere protein B (CENP-B) binding motif, suggest that the satII DNA may represent the most important satellite DNA family that might be involved in the centromeric function in Cervidae. The absence or low intensity of satellite DNA FISH signals on biarmed chromosomes probably reflects the evolutionary reduction of heterochromatin following the formation of chromosome fusions. The phylogenetic trees constructed on the basis of the satellite I-IV DNA relationships generally support the present cervid taxonomy.

• Klíčová slova
• FISH, centromere, cervid phylogeny, satellite DNA, sequencing,
• MeSH
• centromera genetika   MeSH
• heterochromatin genetika   MeSH
• hybridizace in situ fluorescenční metody   MeSH
• lidé MeSH
• přežvýkavci genetika   MeSH
• repetitivní sekvence nukleových kyselin genetika   MeSH
• satelitní DNA genetika   MeSH
• variabilita počtu kopií segmentů DNA genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• heterochromatin MeSH
• satelitní DNA MeSH

The evolutionary clade comprising Nanger, Eudorcas, Gazella, and Antilope, defined by an X;BTA5 translocation, is noteworthy for the many autosomal Robertsonian fusions that have driven the chromosome number variation from 2n = 30 observed in Antilope cervicapra, to the 2n = 58 in present Eudorcas thomsoni and Eudorcas rufifrons. This work reports the phylogenetic relationships within the Antilopini using comprehensive cytogenetic data from A. cervicapra, Gazella leptoceros, Nanger dama ruficollis, and E. thomsoni together with corrected karyotypic data from an additional nine species previously reported in the literature. Fluorescence in situ hybridization using BAC and microdissected cattle painting probes, in conjunction with differential staining techniques, provide the following: (i) a detailed analysis of the E. thomsoni chromosomes, (ii) the identification and fine-scale analysis the BTA3 orthologue in species of Antilopini, and (iii) the location of the pseudoautosomal regions on sex chromosomes of the four species. Our phylogenetic analysis of the chromosomal data supports monophyly of Nanger and Eudorcas and suggests an affiliation between A. cervicapra and some of the Gazella species. This renders Gazella paraphyletic and emphasizes a closer relationship between Antilope and Gazella than what has previously been considered.

• MeSH
• antilopy klasifikace   genetika   MeSH
• biologická evoluce MeSH
• centromera genetika   MeSH
• fylogeneze MeSH
• genová přestavba MeSH
• hybridizace in situ fluorescenční MeSH
• karyotypizace MeSH
• klonování DNA MeSH
• malování chromozomů MeSH
• molekulární evoluce MeSH
• pohlavní chromozomy genetika   MeSH
• satelitní DNA genetika   MeSH
• savčí chromozomy genetika   MeSH
• skot MeSH
• translokace genetická MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• skot MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• satelitní DNA MeSH