Quantification of Aromatase and 5α-Reductase During Gonadal Development in Trachemys scripta, a Reptile with Temperature-Dependent Sex Determination
Loading...
Authors
McQuade, Ryan S.
Issue Date
1996
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
In many reptiles, the incubation temperature of the egg determines the
sex of the offspring. The red-eared slider turtle, Trachemys scripta, shows
such a pattern of sex determination, known as temperature-dependent sex
determination (TSD). At temperatures below 28.6° C all male hatchlings are
produced, while above 29.5° C all female hatchlings are produced; in the
intermediate range a mixed sex ratio is observed.
Previous research has supported the hypothesis that temperature
effects sex determination by activating genes which code for enzymes in
hormone metabolism, which through their action alter the hormone
microenvironment of the embryo. The enzymes aromatase and 5α-reductase,
which convert testosterone to estradiol and dihydrotestosterone, respectively,
have been shown to be important in TSD. Administration of chemicals which
inhibit these enzymes during the temperature-sensitive window of embryonic
development leads to sex reversal in the offspring. Inhibition of aromatase
creates a male phenotype at female-producing temperatures, while inhibition
of 5α-reductase creates a female phenotype at male-producing temperatures.
The relative amounts of these enzymes in embryonic gonadal tissue
from different incubation temperatures before, during, and after sex
determination are being assayed by incubating tissue homogenate with 3 H-
testosterone and isolating the radioactive products using both TLC and HPLC.
Description
v, 22 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.