The present investigation involves the meiotic studies on 11 populations of Achyranthes bidentata Blume (family Amaranthaceae) from western Himalaya, India. The cytological analysis revealed the existence of two cytotypes i. e. plants with chromosome number 2n=42 and 2n=84 based on base number x=7. Among the presently investigated plants, meiotic course was abnormal in hexaploid populations while was normal in the dodecaploid populations. It is first report of cytomixis in Achyranthes bidentata Blume. Morphological analysis revealed three distinct morphotypes among these populations i.e. green stem green bracteoles, green stem purplish bracteoles and purplish stem green bracteoles.
Chromosomal aberration assessment is an important index in mutation breeding for determining the mutagen potency, which helps to deduce an optimum level of mutagen dose tolerable by the species. The current experiment was carried out to study the comparative account of different concentrations of EMS (0.01%, 0.02%, 0.03% and 0.04%), gamma rays (100Gy, 200Gy, 300Gy and 400Gy) and their combinations (100 Gy + 0.01% EMS, 200 Gy + 0.02% EMS, 300 Gy + 0.03% EMS and 400 Gy + 0.04% EMS) on induced chromosomal aberrations in two varieties of Vicia faba L. viz; PRT-12 and vikrant. The control plants showed normal meiosis while the treated plants showed considerable meiotic anomaly. Percent frequency assessment showed dose dependent increase in aberrations. The different abnormalities observed were laggards, bridges, stickiness, micronuclei, disturbed polarity, cytomixis etc. Seeds treated with combination treatments showed more cytological aberrations then individual treatments of both gamma and EMS doses. The order of the most signifi cant dose from each treatment conditions (physical, chemical and combination) were 300 Gy + 0.03% EMS > 400 Gy > 0.04% EMS for var. vikrant and 400 Gy + 0.04% EMS > 0.04% EMS > 400 Gy for var. PRT-12. The comparative analysis showed higher sensitivity of variety vikrant towards the doses of mutagen used than variety PRT-12 at same dose.
In the Japanese rice frog, Fejervarya kawamurai, we identified two unusual features of the sex ratio using artificial crosses at laboratory. Firstly, inbreeding such as sibling-sibling crosses, backcrosses, and diploid gynogenesis resulted in a male-biased sex ratio with a high rate of developmental mortality. Secondly, outbreeding reduced the mortality, and particularly outbreeding of females with males from a geographically separate population restored the sex ratio. Established mechanisms of genetic and environmental sex determination in vertebrates do not easily explain these results. Ecologically, this mechanism favors expanding populations that invade new habitat, because frogs must move continuously between populations to produce enough daughters and reduce embryonic mortality.
Two sympatric forms of the Siberian lenok genus Brachymystax, sharp-snouted lenok (B. lenok, SS) and blunt-snouted lenok (B. tumensis is applied currently, BS), from the Amur River basin shared similar karyotype showing 2n = 90 and the formula of 8M+1SM+1SM-ST+9ST+27A, with NF = 110. However, AgNORs were located on one each pair of acrocentric and subtelocentric chromosomes in the SS lenok, and only one pair of subtelocentric chromosomes in the BS lenok. The observed karyotypic difference strongly supported these two forms to be different species. Variations of previously published lenok karyotypes also were discussed.
When we look at Asian countries, with all their unique cultures and histories, we can be proud of our traditions, so different from country to a country. In contrast, science requires universality from us. However, until the end of 20th century, there was no such a common forum for chromosome science in Asia. In 1998, while the 18th International Congress of Genetics was being held in Beijing, China, chromosome researchers attending from Japan (Dr. Kiichi Fukui), China (Dr. Youzhi Ma), Korea (Prof. Jae-Wook Bang) and Thailand (Dr. Somsac Apisitwanich) discussed the possibility of creating an Asian forum for chromosome researchers. An enthusiastic discussion followed and unanimously concluded with the decision to have the first Asian Chromosome Colloquium (ACC) at Beijing. One of the reasons why an ACC was agreed upon is that there was already a long tradition of bilateral conferences between China and Japan initiated in 1987 at Beijing (Hong 1989) and in 1992 at Tianjin (Tanaka 1992) by Profs. Hao Shui (Northeast Normal Univ.), Chen Ruiyang, (Tianjin Univ.), Hong Deyuan (Inst. Botany, Academia Sinica) Ryuso Tanaka, Kenji Taniguchi, and Masashi Nakata (Hiroshima Univ.). We always stand on the shoulders of the giants.
Microscopy methods have provided most of our knowledge to date on the structural organisation of chromosomes. Even after decades of research, the high order structure of human chromosomes is still under investigation. The new generation of X-ray sources, X-ray Free Electron Lasers (XFELs) have opened an opportunity for imaging these complex structures with higher than optical resolution but without the radiation damage that usually accompanies X-ray imaging. Here we report our first experimental steps towards imaging micron-sized human chromosomes using the SACLA XFEL facility in Japan using the MAXIC chamber. The paper highlights the sample preparation of chromosomes, staining and drying conditions used, as well as the imaging optimisations and shows our fi rst results.
Polyamine chromosomes in solution are used for various applications where the quality of the isolated chromosomes used as starting material is a key factor. Here we describe our current efforts for obtaining a single chromosome using microfl uidics and collecting using a robotic device. Beads of similar size to the hydrodynamic radius of chromosomes were used to characterize and describe the instrumentation development as well as to aid in future improvements as needed. The procedures described here have the potential to provide a rapid and efficient way to isolate highly pure human chromosomes as starting material for many applications thus offering exciting new possibilities.
Allopolyploid resynthesized Brassica napus (AACC, 2n = 38) was produced by cross-hybridization between B. rapa (AA, 2n = 20) and B. oleracea (CC, 2n = 18) for new vegetative crop breeding. Many studies have provided evidences for the phenotype instability and close relationship between A and C genome in the amphidiploid resynthesized B. napus cultivars. In fact, a new B. napus varieties, Hanakkori showed atypical morphological characters and generated many off-type progeny plants. In this study, we investigated the pollen fertility, chromosome number, structure, and behavior linked to define the factors, which produce the unstable phenotypic expressions in the Hanakkori progenies. We define the chromosome number and chromosome organization using fluorescence in situ hybridization analysis on somatic mitosis and meiosis cells. Off-type plants with lower pollen fertility show the instability of chromosome number and structures with small chromosome fragments. Observation of chromosomes behaviors at meiosis showed that the meiotic division in off-type plants led to appreciably higher abnormalities than in on-type plants. These results demonstrated that minimized abnormal chromosome structure and formation might be essential to stabilize the normal progenies in the B. napus plant breeding.
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