EFFECT OF CAFFEINE ON RING CHROMOSOME X LOSS AND NON-DISJUNCTION IN UNDERNOURISHED DROSOPHILA MELANOGASTER ADULTS

Resumen

The mutagenic effect of caffeine has been demonstrated in several animal and plant species, including human cells in tissue culture. For such studies, whose aim is to find gene-controlled repair mechanisms, Drosophila melanogaster with its well-known genetics is a suitable test system. The induction of recessive lethals in Drosophila by feeding the larval with special food, has been reported by several investigators and refuted by others.
An improved method was used for detecting X or Y chromosome loss and non-disjunction in both sexes of Drosophila melanogaster by identifying the exceptional progeny recovered. Females from the stock y²wª/ sc⁸Y; e/e were collected as virgins and stored in a complete food medium or in an incomplet food medium i.e., without yeast, which is the main nutritive component of the Drosophila food. The stock which provided males had an sc⁸Y chromosome and a closed ring X^c2 chromosome with the markers yellow and Bar.
Continuously well-fed flies showed no increase in X or Y chromosome loss or in non-disjunction whereas those adults fed with normal nutrient with caffeine added, showed significantly higher frequencies of X or Y paternal chromosome loss. No change was found in maternal X chromosome loss or in the non-disjunction of sex
chromosomes in both parents. On the other hand, undernourished adults gave paternal X or Y chomosome loss rates which were significantly higher than those obtained in the well nourished groups.
The joining of the broken ends of sperm chromosomes is normally delayed until fertilization is over, hence, undernourishment seems to affect the repair mechanism contained in the egg, due to modifications in the physiological environment of the oocytes, as discussed below in this paper.
The undernourishment of females fed on nutrient with caffeine added and mated to normally fed males produced a decrease in the rate of paternal sex chromosome loss, as compared to undernourished females without caffeine.
The data obtained can be interpreted according to the hypothesis that mutational enhancement by undernourishment, as well as the contradictory effects of adding caffeine to complete and incomplete media are associated with some restriction in the fertilized egg on the joining of the paternal chromosome ends produced previously by breakage in the sperm.