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C-banding karyotype and relationship of the dipodids Allactaga and Jaculus (Mammalia: Rodentia) in Egypt

100%

Shahin A. A. B. , Ata A. T. M.

tom 52

nr 1-2

25-31

The C-banding karyotype of the jerboas Allactaga tetradactyla, Jaculus jaculus jaculus, and Jaculus orientalis was described and interspecific relationships were discussed. Despite the conservation of a relatively small amount of C-heterochromatin located at the centromeric region of some chromosomes in all karyotypes, a striking loss of C-heterochromatin was clearly observed in J. orientalis. C-bands were totally absent in 33 of the 48 chromosomes of J. orientalis, compared to only 7 for J. j. jaculus and 11 for A. tetradactyla. The differences in C-banding amongst karyotypes of the three species were attributed either to transformation of heterochromatin into euchromatin or vice versa, deletion of heterochromatic segments resulting from pericentric inversions, or to variation of euchromatin content and its correlation with the chromosome size and arrangement of heterochromatin. The present findings are consistent with the main hypotheses derived from morphological, chromosomal, and biochemical data that the genera Allactaga and Jaculus have independently developed from a common ancestral form and that J. jaculus and J. orientalis are both distinct congeneric species, but revealed that the C-banding karyotypes of both J. j. jaculus and J. orientalis are distantly related to each other. Therefore, it is concluded that the karyotype of J. j. jaculus may be ancestral and that of J. orientalis may have derived from it.

A comparative analysis of the rate of meiosis, chiasma frequency and terminalization in the Jerboas Allactaga and Jaculus (Rodentia: Dipodidae) in Egypt

86%

Ata A. T. M. , Shahin A. A. B. , Allam H. Z.

Folia Biologica

2001

tom 49

nr 3-4

129-135

The rate of seven meiotic stages (zygotene-pachytene, diplotene-diakinesis, metaphase I, anaphase I, metaphase II, anaphase II, and quartet) was studied in the jerboas Jaculus jaculus jaculus, Jaculus orientalis, and Allactaga tetradactyla, chiasma frequency and terminalization being examined only in J. jaculus and J. orientalis, and compared with the previous data concerning A. tetradactyla. Significant differences in the rate of meiosis, frequency of bivalent types, and frequency of interstitial and distal or terminal chiasmata per genome length were observed between A. tetradactyla and the two congeneric species J. jaculus and J. orientalis. Differences of these parameters among individuals within each species are also discussed in detail.