PubMed · 394428
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L U Lamm, G B Petersen. 1979. The HLA genetic linkage group.. https://pubmed.ncbi.nlm.nih.gov/394428/
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Hippophae rhamnoides ssp. turkestanica, a subdioecious plant inhabiting the cold desert of the Indian Himalaya, has gained immense recognition for its nutritional and medicinal values. In recent years, the plant species has proven to be a suitable system to understand the evolution of dioecy. Despite its biological significance, the cytogenetics of this dioecious plant is unclear due to various conflicting accounts of its X-Y chromosome system, particularly the length of Y-chromosome. In this study, we resolved these ambiguities through comprehensive cytogenetic analyses across diverse western Himalayan populations. Using morphometric analysis and fluorescence in situ hybridization (FISH) with a gender-specific marker (HRMSSR), we confirmed homomorphic XX chromosomes in females and heteromorphic sex-chromosomes in males with a notably smaller Y-chromosome. The investigation also revealed a predominant somatic chromosome number of 2n = 24, although minor deviations (2n = 18, 20, 22) appeared at the seed level. These findings highlight an evolutionarily advanced sex-chromosome system. This first detailed cytogenetic investigation of Himalayan Seabuckthorn provides critical insights into the chromosomal architecture, laying a crucial foundation for future evolutionary, genomic, and conservation studies in the species.
A functional copy of the alpha mating type gene of Saccharomyces cerevisiae has been cloned by transformation in yeast. Using the Southern Blotting procedure it has been shown that three distinct genetic loci implicated in mating type interconversion (HML, HMR and MAT) contain sequences homologous to the clone fragment. The restriction fragment associated with each locus exhibits a characteristic size which can be correlated with the mating type allele present at that locus. The characteristic size difference between the a and alpha genetic elements made it possible to demonstrate that the homothallic interconversion of mating types in this yeast occurs by DNA rearrangement as proposed in the 'cassette hypothesis'.
By classical genetic experiments, evidence is provided that the male recombination factor, 31.1 MRF, has the ability to be transposed to another chromosome. The procedure by which the transposition occurs must be different from that of classical crossing over. It appears that transposition occurs only when the factor is active in male germ cells. Moreover, the factor appears to be able to undergo successive transpositions. Furthermore, the integration sites of the factor, when transposed into another chromosome, may not be completely random. Finally, the third chromosome of the 31.1/CyL4 strain can also induce male recombination.