Minichromosomes in Drosophila melanogaster derived from the transposing element TE1.
A minichromosome has originated from the transposing element TE1. This autonomously replicating chromosome contains the structural genes white and roughest, from the Drosophila X chromosome. It arose within a stock carrying TE1 at 45F on chromosome 2. In addition to the w and rst genes, the minichromosome may carry section 45C-45F from chromosome 2. It is inherited by 33%-47% of the offspring. By this criterion it carries a centromere, although the origin of the centromere is unknown. From this minichromosome a still smaller one has originated, probably through the loss of all material from chromosome 2 together with some heterochromatin. At the same time a duplication of white and roughest could have taken place. This chromosome has a strange morphology and is more frequently lost in meiosis than the larger one, but is still transmitted to about 29%-37% of the progeny of one parent heterozygous for the minichromosome. In both cases the flies have variegated eyes, probably as a result of position-effect variegation. The variegation pattern is influenced by factors in the X chromosome. The size of the smaller minichromosome is little more than 1 Mb as determined by pulsed field gel electrophoresis.
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Department of Genetics, University of Göteborg, Sweden.
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D000818:Animals; D005075:Biological Evolution; D003001:Cloning, Molecular; D003434:Crossing Over, Genetic; D004251:DNA Transposable Elements; D004331:Drosophila melanogaster / Q000235:genetics*; D014960:X Chromosome / Q000648:ultrastructure*
D004251:DNA Transposable Elements