Biology Reference
In-Depth Information
4
Sterility and Mutants
The role played by gonads and their genes in the process of sex
differentiation is realized in their absence. Gonadectomy is one of the
earliest techniques used to know the role played by the gonads and their
hormones in sex differentiation. Because of their rarity and inability to
function, the abnormal hermaphrodites, though an important resource,
have so far not received much attention. This is perhaps true of the steriles
too. Morbid embryos, caused by one or another mutant gene, have long
been reported. However, the mutants, especially the viable ones, have
begun to receive their due attention by medical and molecular biologists
since this millennium. This section broadly indicates their occurrence and
importance in our understanding of the process of differentiation including
sex differentiation.
4.1 Gonadectomy
Castration/ovariectomy is one of the earliest techniques employed to
understand the role of hormones in sexualization of the gonad. Turner (1947
cited in Atz, 1964) has reported the complete regeneration of gonopodium
in castrated
Gambusia affi nis
with regenerated testis as small as 4% of the
normal size. Clearly, the very presence of the masculinizing hormone like
11β-hydroxytestesterone (see Table 1) in the small regenerating testis is
adequate for regeneration of the gonopodium. Impressed by the fi ndings
of Noble and Kumpf (1937 cited in Atz, 1964), the zealous Reinboth (cited
in Atz, 1964) recorded the apparently accelerated appearance of testis in
a unilaterally ovariectomized protogynic female
Coris julis
beginning to
change sex. A better designed gonadectomy in
C. julis
, which is amenable
to surgical gonadectomy, may prove to be rewarding.
