CHROMOSOMAL DISTRIBUTION AND POPULATION-DYNAMICS OF THE 412 RETROTRANSPOSON IN A NATURAL-POPULATION OF DROSOPHILA-MELANOGASTER

The localization of the insertion sites of the 412 retrotransposable e lement was analysed by in situ hybridization to the polytene chromosom es of the genomes of males from a natural population of Drosophila mel anogaster. Non-parametric statistical, tests do not reveal any particu lar distribution of the insertion sites over the chromosomes, suggesti ng an apparently random distribution of the 412 element. Aggregation a nd dispersion tests were highly significant with data of copy number ( when all genomes are pooled, many copies may be at a given site), sugg esting the existence of sites with high insertion frequency. Compariso n with other data from the literature confirms the tendency for a low proportion of insertions on the X chromosome in comparison with the au tosomes, a result in agreement with selection acting against the detri mental effect of the 412 element insertions.