Indian Society of Genetics & Plant Breeding

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PACHYTENE ANALYSIS IN ORrZA-I. CHROMOSOME MORPHOLOGY IN ORrZA SATIVA

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KARYOMORPHOLOGICAL studies -in plants are confined to three stages-somatic
metaphase in root tips, pollen mitosis, and pachytene. The first method has yielded
valuable cytotaxonomical data in several taxa where the chromosome size is large enough
and the karyological differences between related species are distinct. This approach
is almost unrewarding in species with small chromosomes. Studies on pollen
mitosis have an advantage over the former method, since only the haploid complement
need be analysed and the problem of matching the homologous chromosomes is absent.
However, in both these methods, the maximum data that could be secured is limited
to gross changes in the symetry of the karyotype, the number of satellited chromosomes
etc. Pachytene analysis, in addition to providing all this information, has the unique
advantage of enabling a critical study of the chromomere pattern and other fine details
of the different regions of the bivalents, thereby giving supplementary evidence
to the data collected from the study of mitoses in root tips and pollen grains. Further,
pachytene studies help to uncover the presence of differential segments, duplications
and deletions which can only be inferred by the other methods. Smallness of the
chromosomes is often an advantage in the pachytene analysis and hence in plants where
the chromosome size constitutes a limiting factor for study of root-tip metaphases, this
method has a great utility.
  

Info

Year: 1960
Volume: 20
Issue: 1
Article DOI: NA
Print ISSN: 0019-5200
Online ISSN: 0975-6906

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