This Week in Science 4-25-14

By Amanda Spadaro

Science Editor

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Scientists have now determined when they believe that the sex chromosomes in humans appeared, approximately 180 million years ago. While there are obvious biological differences between the sexes, they are all dependent on the presence of the Y chromosome, which is what determines maleness. Researchers initially believed that the Y chromosome evolved from the X chromosome, but current research suggests that these sex genes appeared because of changes in global temperature. University of Lausanne’s Swiss Institute of Bioinformatics sampled male tissue samples from three major mammalian lines to compare them female tissue genetic sequences.

This analysis allowed researchers to determine which genes are specific only to males, the Y chromosome. This identified a sex-determining gene, called SRY, which has been seen in sequences of common ancestors dating back 180 million years. A second gene, AMHY, responsible for the Y chromosome emergence in monotremes appeared around 175 million years.

One current idea is that changes in temperature may have affected the emergence of these genes, especially because of the modern-day effects of temperature determining sex in current reptile species.

The mantis shrimp, a stomatopod that is one of the strongest animals, has inspired the production of a new design for composite materials. The new design, developed by scientists under David Kisailus at the University of California, is stronger than current aircraft material and more resilient to wear than previous designs.

This shrimp, despite being less than six inches long on average, has strong biological durability that intrigued Kisailus. The shrimp possesses an appendage that works to crush prey, moving faster than a .22 bullet. This force can be up to 1,000 times the shrimps own body weight without causing damage to the appendage itself.

The research focused on the appendage’s structure, studying how layers of material interact to allow for such strength.  The pattern, called helicoidal arrangements, has layers aligning at specific angles relative to each other, between 10 to 25 degrees. During experimental testing to examine the strength, the new design showed 15 to 20 percent more durability than current composite material patterns.

“These findings have implications in the design of composite parts for aerospace, automotive, and armor applications,” the researchers wrote in their article, published in the journal “Acta Biomaterialia.”  Scientists hope to use the naturally-occurring materials in biological organisms to expand work on devising the optimal properties for composite materials.

International scientists have now identified a single genetic mutation that may cause a rare brain disorder, specifically affecting families in Turkey. Two independent teams of scientists have identified the mutation: one team from Baylor College of Medicine and the Austrian Academy of Sciences and the other from Yale University, the University of California San Diego, and the Academic Medical Center in the Netherlands.

In Eastern Turkey, marriages between relatives as close as first cousins is common and populations in the area have shown unexplained neurological disorders which may be the result of genetic defects. A single genetic mutation called CLP1 is believed to be responsible and when children inherit two defective copies of the gene, the health of their nerve cells may be affected. Experimentally, both mice and humans with the genetic mutation demonstrated similar effects while mice trials showed that the CLP1 gene handles the development or survival of brain stem cells.  Those children who are affected experience progressive muscle weakness, be unable to speak and have small, malformed brains. In addition, these children can be at a higher risk for having seizures.

Genetic analysis suggests that the genetic mutation began spontaneously in four, unrelated families approximately 400 years ago. The scientists emphasized that in the Middle East, where marriages between closely related individuals, children may be more susceptible to these types of random, negative mutations.