The observation “was kind of fortuitous,” says Deveson, a biologist at the Garvan Institute of Medical Research in Sydney. But in sex-reversed females, one of the sections normally removed remained. RNA carries information from DNA that gets translated in proteins, and normally it gets edited before translation - certain sections get taken out. During a cursory skim through the RNA data for JARID2 and JMJD3, study coauthor Ira Deveson noticed something strange. The researchers also found changes in the lizard’s RNA. Another is involved in X chromosome inactivation, which ensures that females don’t get a double dose of proteins made by genes housed on their pair of X chromosomes. For instance, in mammals, a Jumonji gene interacts with SRY, a gene on the Y chromosome that sets off testes development in males. Two, JARID2 and JMJD3, are part of a family of genes called the Jumonji family, which are known to influence sex differentiation in other animals. Sex-reversed females turned up the activity of several genes, the researchers found. Then, the researchers compared that RNA, looking for differences in the ways the lizards were turning on genes. The team collected RNA from the brain, reproductive organs and other tissues of normal female, normal male and sex-reversed female Australian central bearded dragons ( Pogona vitticeps). “They have two sex chromosomes, but they also have this temperature override,” Holleley says.īy comparing bearded dragons that are female because of their chromosomes and those that are female because of environmental influences, Holleley and her colleagues hoped to sort out genetic differences that might point to how the lizards make the switch. But as temperatures creep above 32°, chromosomally male ZZ dragons will reverse course and develop as females instead. When eggs are incubated below 32° Celsius, embryonic bearded dragons with two Z chromosomes develop as male, while dragons with a Z and a W chromosome develop as female. Bearded dragon lizards are an unusual case because chromosome combinations and temperature are known to influence sex determination, says ecologist Clare Holleley of the Commonwealth Scientific and Industrial Research Organisation in Canberra, Australia ( SN: 7/25/15, p.7).
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