Chromosomal instability plays a significant role in karyotype evolution and speciation in mammalian groups with notable intraspecific chromosomal variation. The Cervidae family, known for its rapid karyotypic evolution due to chromosomal fragility, shows substantial chromosomal diversity, making it a focal point for studies on chromosomal evolution, particularly with respect to conservation and taxonomic classification. The Amazon gray brocket deer (Passalites nemorivagus) exhibits pronounced chromosomal polymorphism, including two distinct sex chromosome systems: the ancestral XX/XY system and a new system due to an X-autosome fusion (neo-X), where males present XY1Y2. This variation is intriguing, especially given that the effects on hybrids have not been previously reported. This study uses bovine whole-chromosome painting (WCP) and BAC probes to document karyotypic variation in P. nemorivagus. A male with the XY system and a heterozygous autosomal Robertsonian fusion was paired with a female with neo-X chromosomes, and the resulting female offspring displayed an X-autosome fusion in heterozygosity. The females in this study, hybrids for the sex system, exhibited estrus, copulated, and both gave birth to offspring. This characterization is the first step in investigating the effects of sex chromosome system variation on hybrid viability and fertility, and provides insights into the reproductive biology of Neotropical deer.

• Klíčová slova
• Cervidae, chromosome rearrangement, conservation, cytogenetics, sex chromosome,
• Publikační typ
• časopisecké články MeSH

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

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

Homologous chromosomes exchange genetic information through recombination during meiosis, a process that increases genetic diversity, and is fundamental to sexual reproduction. In an attempt to shed light on the dynamics of mammalian recombination and its implications for genome organization, we have studied the recombination characteristics of 112 individuals belonging to 28 different species in the family Bovidae. In particular, we analyzed the distribution of RAD51 and MLH1 foci during the meiotic prophase I that serve, respectively, as proxies for double-strand breaks (DSBs) which form in early stages of meiosis and for crossovers. In addition, synaptonemal complex length and meiotic DNA loop size were estimated to explore how genome organization determines DSBs and crossover patterns. We show that although the number of meiotic DSBs per cell and recombination rates observed vary between individuals of the same species, these are correlated with diploid number as well as with synaptonemal complex and DNA loop sizes. Our results illustrate that genome packaging, DSB frequencies, and crossover rates tend to be correlated, while meiotic chromosomal axis length and DNA loop size are inversely correlated in mammals. Moreover, axis length, DSB frequency, and crossover frequencies all covary, suggesting that these correlations are established in the early stages of meiosis.

• Klíčová slova
• Bovidae, Crossovers, MLH1, Meiosis, RAD51, Recombination,
• MeSH
• dvouřetězcové zlomy DNA MeSH
• meióza * MeSH
• MutL homolog 1 MeSH
• myši MeSH
• přežvýkavci genetika   metabolismus   MeSH
• rekombinace genetická * MeSH
• rekombinasa Rad51 MeSH
• savčí chromozomy metabolismus   ultrastruktura   MeSH
• synaptonemální komplex metabolismus   ultrastruktura   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• MutL homolog 1 MeSH
• rekombinasa Rad51 MeSH