ISSN:
1432-0886
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract In a sample of 85 males of the grasshopper Melanoplus femur-rubrum, three different supernumerary chromosomes (B-chromosomes) were observed: a medium-sized metacentric, BM, present in 12.9% of the males and two small telocentrics, BT and Bt, present in 8.2% and 3.5% of the males, respectively. The BM element is mitotically stable, while the BT and Bt elements are mitotically unstable, exhibiting numerical variation among testicular follicles. The mean number of B's per male (testis) is 1.00, 1.62, and 1.38 for the BM, BT, and Bt elements, respectively. A study of chiasma frequency among A-chromosomes revealed that there are no significant differences among the zero B and various B classes either for chiasma frequency or for the variation in chiasma frequency between individuals. There was, however, evidence for a higher within-individual variation in B-containing males when these were pooled. Cells with two Bt-chromosomes were regularly missing the smallest pair of A-chromosomes, suggesting that the Bt element induces non-disjunction of a pair of A-chromosomes and, possibly, that the Bt-chromosome is derived from the missing A-chromosome.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00290927
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