Genetic effect of norgestrel treatment and X-irradiation on drosophila melanogaster
Since Auerbach and Robson (1946) reported for the first time that mustard gas has a mutagenic activity as well as ionizing radiation (Muller, 1927), a number of chemical compounds have also been shown to be mutagenic in many organsims ranging from viruses to man.
Recently, it has been shown that a synthetic ovarian steroid, Lyndiol 2.5, has the mutagenic effects in Drosophila (Kim and Yoon, 1969), and that in insects a molting hormone alters the rate of mutations induced by X-radiation (Burdette and Yoon, 1967).
Meanwhile, although most of the experimental work on induced mutations has been performed with organisms such as Drosophila and mice, there is no reason to think the results would not be applicable to humans as well.
In view of the above findings the author studied the genetic effects of the synthetic steroid, norgestrel, and tested its effect on the rate of mutations induced by X-radiation in Drosophila melanogaster. The large series of experments were divided into the following four groups.
Group A : Treated with norgestrel only
The male files were raised on a medium containing 0.02 M norgestrel throughout the larval, pupal and imaginal stages of development.
Group B : Irradiated with X-ray (1,500r) only
The male flies were irradiated with 1,500r of X-rays (Maxiamr 250-Ⅲ, 220 KVP, 15mA, Filter: Th. Ⅱ) approximately 4∼6 hours old after eclosion.
Group C : Irradiated with X-ray (1,500r) after norgestrel treatment
Norgestrel (0.02M) was given as for Group A, and then the male flies were irradiated with 1,500r as in Group B.
Group D : Control
All the experimental processes were carried out at 25±1℃ on the normal medium consisting of E.B. Lewis' (Pasadena standard corn meal medium) in the standard vials and bottles.
The treated male flies (sc**8·Y·B**S/y w**ict**gf**1) of all groups were crossed individually to 2 or 3 multipurpose virgin flies(y sc**S1 In49 sc**8;dp bw;st p**p), and were tested through the successive two generations.
From the data obtained, it is possible to make the following conclusions;
1) Norgestrel is mutagenic in Drosophila. In the group treated with norgestrel, an increased rate of sex-linked recessive lethals(0.2%), nondisjunction(0.25%), and other visible mutations(0.10%) were found, while the F^^1 sterility and the loss of Y chromosome did not differ from those of controls.
2) The pretreatment with norgestrel protected the flies against the loss of the Y chromosome but did not protect them against the F^^1 sterility caused by X-radiation.
3) Norgestrel may have additive effects on the X-ray induced gentic damage such as chromosomal nondisjunction, and sex-linked recessive lethality.
4) Norgestrel may help to rejoin the ends of chromosomes broken by the X=radiation.
5) The mechanism of genetic damage by norgestrel is somewhat different from that induced by other mutagenic chemicals.