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Baby Turtle Turns Into a Male, Adding Fresh Dimensions to Temperature-Dependent Sex Determination Theory

Inching closer to cracking the 50-year-old puzzle of how temperature turns baby turtles male or female, researchers have uncovered a molecular link that connects temperature with sexual development. In turtles and other reptiles, whether an egg hatches male or female depends on the temperature of its nest.

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The phenomenon was first discovered in reptiles more than 50 years ago, but until now the molecular details were a mystery.
turtle, representational image, pixabay

Inching closer to cracking the 50-year-old puzzle of how temperature turns baby turtles male or female, researchers have uncovered a molecular link that connects temperature with sexual development.

In turtles and other reptiles, whether an egg hatches male or female depends on the temperature of its nest.

The phenomenon was first discovered in reptiles more than 50 years ago, but until now the molecular details were a mystery.

In a study published in the journal Science, the researchers said they have finally identified a critical part of the biological “thermometer” that turns a developing turtle male or female.

The explanation lies not in the DNA sequence itself — the A’s, T’s, C’s and G’s — but in a molecule that affects how genes are expressed without altering the underlying genetic code, the researchers said.

"This is the first functional evidence of a molecular link that connects temperature with sexual development," Capel said.
turtle eggs, pixabay

“Temperature-dependent sex determination has been a puzzle for a really long time,” said Blanche Capel, Professor at Duke University in North Carolina, US.

“This is the first functional evidence of a molecular link that connects temperature with sexual development,” Capel said.

Unlike humans and most other mammals, the sex of many turtles, lizards, and alligators is not determined by the chromosomes they inherit, but by ambient temperatures during a sensitive stage of development.

For a common pond and pet turtle called the red-eared slider, for example, eggs incubated at 32 degrees Celsius produce all female hatchlings, while those kept at 26 degrees Celsius hatch as males.

In the study, the researchers showed that cooler egg incubation temperatures turn up a key gene called Kdm6b in the turtle’s immature sex organs, or gonads.

This, in turn, acts as a biological “on” switch, activating other genes that allow testes to develop.

Unlike humans and most other mammals, the sex of many turtles, lizards and alligators is not determined by the chromosomes they inherit, but by ambient temperatures during a sensitive stage of development.
turtles, pixabay

To home in on the critical Kdm6b gene, the researchers took a group of freshly laid turtle eggs, incubated them at either 26 or 32 degrees Celsius, and looked for differences in the way genes were turned on in the turtles’ gonads early in development — before their fate as ovaries or testes has been decided.

Further experiments showed that the protein encoded by the Kdm6b gene, in turn, interacts with a region of the genome called Dmrt1, which acts as a master switch to turn on testis development.

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“The next step is to find the temperature-sensing trigger,” said study co-author Ceri Weber, a Ph.D. candidate in the Capel lab at Duke.

“We’re trying to narrow down the possibilities,” Weber added. (IANS)

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Development of Alzheimer’s Disease Not Totally Linked to Genetics: Study

The research team analyzed the gene sequence and the biological age of the body's cells from blood

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Genetics
With additional funding, researchers could further explore the interaction between Genetics and environment in the development of Alzheimer's disease and the impact of environmental factors in delaying the onset of this disorder. Pixabay

The colour of our eyes or the straightness of our hair is linked to our DNA, but the development of Alzheimer’s disease isn’t exclusively linked to Genetics, suggest new research.

In the first study published about Alzheimer’s disease among identical triplets, researchers found that despite sharing the same DNA, two of the triplets developed Alzheimer’s while one did not.

The two triplets that developed Alzheimer’s were diagnosed in their mid-70s, said the paper published in the journal Brain.

“These findings show that your genetic code doesn’t dictate whether you are guaranteed to develop Alzheimer’s,” said Dr Morris Freedman, head of neurology at Baycrest Centre for Geriatric Care.

“There is hope for people who have a strong family history of dementia since there are other factors, whether it’s the environment or lifestyle, we don’t know what it is, which could either protect against or accelerate dementia.”

All three, 85-year-old siblings had hypertension, but the two with Alzheimer’s had long-standing, obsessive-compulsive behaviour.

The research team analyzed the gene sequence and the biological age of the body’s cells from blood that was taken from each of the triplets, as well as the children of one of the triplet’s with Alzheimer’s.

Genetics
The colour of our eyes or the straightness of our hair is linked to our DNA, but the development of Alzheimer’s disease isn’t exclusively linked to Genetics, suggest new research. Pixabay

Among the children, one developed early onset Alzheimer’s disease at age 50 and the other did not report signs of dementia.

The research team also discovered that although the triplets were octogenarians at the time of the study, the biological age of their cells was six to ten years younger than their chronological age.

In contrast, one of the triplet’s children, who developed early onset Alzheimer’s, had a biological age that was nine years older than the chronological age.

The other child, who did not have dementia, of the same triplet showed a biological age that was close to their actual age.

Genetic
Your Genetic code doesn’t dictate whether you are guaranteed to develop Alzheimer’s Disease. Pixabay

“The latest genetics research is finding that the DNA we die with isn’t necessarily what we received as a baby, which could relate to why two of the triplets developed Alzheimer’s and one didn’t,” says Dr. Ekaterina Rogaeva, senior author on the paper and researcher at the University of Toronto’s Tanz Centre for Research in Neurodegenerative Diseases.

“As we age, our DNA ages with us and as a result, some cells could mutate and change over time”.

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With additional funding, researchers could further explore the interaction between genetics and environment in the development of Alzheimer’s disease and the impact of environmental factors in delaying the onset of this disorder. (IANS)