Isolation of Visible Genetic Mutants of Drosophila Ananassage In Sri Lanka

Abstract

Attached

1. A study was carried out to isolate morphological mutants from wild populations of D. ananassae in Sri Lanka, and to estimate the mutation load in these wild populations. Seventeen mutants of spontaneous origin were isolated.

2. In the case of collections from the wild, ten wild male Drosophila ananassae were collected fortnightly from two places close to Colombo, namely, Gangodawila and Nawinna. They were mated individually to virgin females of a wild type laboratory stock in the ratio of one male to one female. The F1 offspring of these crosses were examined and they were allowed to intercross and the resulting F2 progeny were carefully screened for morphological deviants. When such deviants were isolated they were tested genetically to study their mode of inheritance.

3. From this survey, twenty seven phenotypically abnormal types were isolated. Among these, seventeen deviants were truly genetic. Three deviants proved to be phenocopies. Five other deviants which can be described as crippled leg, hooked leg, yellow body colour, arista less, and extended wing were lost before definite tests could be carried out on them.

4. Genetic tests have revealed that seven of the mutants that were isolated are inherited as recessive autosomal gene, four as recessive sex linked genes and only one as a dominant autosomal gene. The seven autosomal recessive mutants are marginal cell cross vein (mov), marginal cell double cross vein (mdcv) wing, demi-wing (dw), reduced eye (re), brown eye (bw), hooked leg (hl), net wing (nt). The four recessive sex linked mutants are namely, marginal cell less wing (mol), semi –wing (sw), balloon semi- wing (bsw), and cut wing (ct), while a single dominant autosomal mutant, namely, Curled wing (CU) was also isolated. The other five mutants, namely, contracted wing (ent), vesiculated wing (VS), notch wing (n), garnet eye (g) and dark antennae (da) were lost before complete tests could be carried out on them. From the limited results of these mutants it is clear that these are also true mutants, but due to the scanty results it is difficult to come to a conclusion regarding their mode of inheritance.

5. The following nine, described as marginal cell cross vein (mcv) wing, marginal cell double cross – vein (mdev), demi-wing (dw), reduced eye (re), not wing (nt), marginal cell – less wing (mcl), semi – wing (sw), ballooned semi – wing (bsw) and curled wing (CU) mutants to my knowledge have not been reported previously and are being reported for the first time.