Hidden DNA fragment the 'trigger switch' for male development
Biology textbooks may need to be re-written, with scientists finding a
new piece of DNA essential to forming male sex organs in mice

Date:
October 2, 2020
Source:
University of Queensland
Summary:
Biology textbooks may need to be re-written, with scientists finding
a new piece of DNA essential to forming male sex organs in mice.



FULL STORY ========================================================================== Biology textbooks may need to be re-written, with scientists finding a
new piece of DNA essential to forming male sex organs in mice.


==========================================================================
An international research collaboration with The University of Queensland
found the Y-chromosome gene that makes mice male is made up of two
different DNA parts, not one, as scientists had previously assumed.

UQ's Institute of Molecular Biosciences Emeritus Professor Peter Koopman
said the critical DNA fragment had been hidden from researchers for more
than 30 years.

"Expression of the Y chromosomal gene Sry is required for male development
in mammals and since its discovery in 1990 has been considered a one-piece gene," he said.

"Sry turns out to have a cryptic second part, which nobody suspected was
there, that is essential for determining the sex of male mice. We have
called the two- piece gene Sry-T." The scientists tested their theory
and found that male mice (XY) lacking in Sry-T developed as female,
while female mice (XX) carrying a Sry-T transgene developed as male.



==========================================================================
The success rate for the experiments was almost 100 per cent.

Emeritus Professor Koopman said the discovery would change how basic
biology and evolution was taught around the world.

"For the last 30 years, we've been trying to figure out how this works,"
he said.

"Sry is a master switch gene because it flicks the switch for male
development, it gets the ball rolling for a whole series of genetic
events that result in a baby being born as a male instead of female.

"This new piece of the gene is absolutely essential for its function;
without that piece, the gene simply doesn't work.



========================================================================== "We've discovered something massively important in biology here,
because without Sry there can be no sexual reproduction and hence no propagation and survival of mammalian species." The discovery may apply
to efforts to manipulate sex ratios in agriculture or for biological pest management. But Emeritus Professor Koopman was quick to point out that,
for ethical and practical reasons, the discovery cannot be utilised on
human embryos.

"Once we understand better how males and females are specified in
non-human species of mammals, then it offers the opportunity to influence
that process," he said.

"The ability to select for the desired sex could dramatically increase efficiencies for agricultural industries such as the dairy industry
(females) or the beef industry (males).

"People have been trying to figure out ways to skew to the desired
sex in these industries for a long time, and now that we understand
more about the fundamental mechanism of Sry it may be possible through
genetic means."

========================================================================== Story Source: Materials provided by University_of_Queensland. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Shingo Miyawaki, Shunsuke Kuroki, Ryo Maeda, Naoki Okashita, Peter
Koopman, Makoto Tachibana. The mouse Sry locus harbors a cryptic
exon that is essential for male sex determination. Science, 2020
DOI: 10.1126/ science.abb6430 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201002105756.htm

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