Attached
Drosophila ananassae was used for the determination of
spontaneous mutation rate in Sri Lanka in a previous study
(Bogahawatte, 1984). The present work was carried out
to study the inheritance patterns of four autosomal mutants
and two sexlinked mutants obtained in the above study at
the Dept. of Zoology, University of Sri Jayewardenepura,
Nugegoda, Sri Lanka. These mutants were bw (brown eye),
"cnt" (contracted wing), hl (hooked leg), mcl (marginal
cel-Iess wing) and ct (cut wing).
This organism was selected for genetical studies as it is
found locally and is easier to breed than D. melanogaster.
Ini tially some experiments were carried out with the purpose
of building up double and triple mutant colonies.
Of the above mutants bw, "cnt" and hl are autosomal mutants
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and of them only brown eye (bw) mutant showed 100%
agreement with Mendelian rules and it is concluded to be
an autosomal recessive gene and the line is pure.
According to Bogahawatte (1984), "cnt" gene is autosomal recessive. However, when IIcnt II was out crossed it gave
rise to only Curled wing flies. When it is inter-crossed
it gave rise to only "cnt" flies and inter-crosses of Curled
wing flies gave rise to wild type, Curled wing and
contracted wing flies in 1:2:1 ratio. Therefore my results
show conclusively that there is no "cnt" gene but that
the IIcnt II phenotype is simply the homozygous form of the
Curled (Cu) gene. They also show the variable expressivity
and incomplete penetrance.
For hooked leg (hl ) mutants, it is concluded that though
it is autosomal recessi ve - according to the inheritance
pattern, it shows variable expressivity and incomplete
penetrance. Their viability is also low.
The sex-linked mutants were cut wing (£!) and marginal
cell-less wing (mcl) whose inheritance patterns were
complex. Each sex-linked mutant when out-crossed or
inter-crossed could produce mcl, .£!.' mcl-ct and wild type
flies in a variable frequency. In order to explain the
aberrant data the following possibilities, namely, pseudoallelism. conditional mutants and movable genetic elements
have been discussed. Pseudo:...allelism probably is not
the concept that could be used to interpret the aberrant
results beause the recombinant types and wild types in
the progeny appear in larger numbers than would be the
case with pseudo-alleles. Also they appear in widly varying
proportions in different test crosses. The concept of the
