Our Science News Update for May 17th
All life on earth is made of four basic nucleic acids: adenine, thymine, cytosine and guanine, which are often known by the respective letters A, T, C and G. These “building blocks” of life make up our DNA, and the DNA of all other life that we know, from the smallest bacterium to the largest whale- that is, until d5SICS and dNaM came along.
d5SICS and dNaM are two synthetic nucleic acids that aren’t naturally found in nature. Much like how adenine and thymine or cytosine and guanine pair together, d5SICS and dNaM forms a third “base pair” in a test tube environment. However, until recently, d5SICS and dNAM have never been part of the DNA code of a live organism.
E. coli is the first exception to this rule. By using a process naturally occurring in some algae, scientists managed to insert d5SICS and dNaM into an E. coli cell, in doing so creating a “semi-synthetic” organism: one made both of naturally occurring nucleic acids and synthetic ones. This change was not permanent, however. As the E. coli cell could not produce the synthetic nucleic acids on its own, it had to be supplied with the nucleic acids from an external source. This acted as a form of control for the experiment, and prevented the modified E. coli from surviving outside of the test tube.
Read more: http://goo.gl/MUEOLi
Not all animals rely on the Y and X chromosomes to determine an individual’s gender before birth. Crocodiles, for example, are determined by environmental temperature while still incubated within an egg. The extent of how far back the Y chromosome goes in mammals is a question that has remained unanswered amongst the scientific community, though a new study could have given us an answer.
By studying the testicular tissue of the three different kinds of mammal- placentals (humans, apes, dogs and cats), marsupials, and monotremes (egg-laying mammals, such as the platypus)- scientists discovered that the Y chromosome evolved twice, once in an ancient ancestor to both placentals and marsupials some 180 million years ago, and again with monotremes 175 years later. It is unknown what caused gender differentiation before the evolution of the Y chromosome, though environmental factors or a different kind of sex chromosome aren’t out of the question.
Learn more here: http://goo.gl/oK5kcK
It’s the “holy grail” in the search for exoplanets, and the mission goal of the Kepler program: to find a earth-sized world in its star’s habitable zone. Kepler 186-f may just be that planet. Orbiting the star Kepler 186, a class M “red dwarf”, Kepler 186-f is the fifth planet and outermost planet in its solar system, with an orbit of 130 days. Because M-class stars are significantly less bright and hot than our own star, their habitable zones are also smaller and closer to the star itself- explaining Kepler 186-f’s close orbit.
It is unknown how old Kepler 186-f is, though M-class stars, which account for some 70% of stars in our galaxy, are notable for being exceptionally long-lasting and stable. It is likely that Kepler 186-f is multiple billions of years old, allowing for life to potentially develop. It should be stated that an earth-sized planet in a star’s habitable zone does not guarantee the existence of life, which as of yet hasn’t been discovered outside of our own planet Earth.
Read more: http://goo.gl/zmGjHN
By analyzing the mitochondrial DNA of modern Native Americans, we know that humans in the New World descend from ancient Asians that lived in Siberia and who crossed the Bering Strait some 18,000 years ago. However, fossil evidence for this is surprisingly lacking, making a recent archaeological discovery- that of a nearly fully intact human skeleton found in an underwater cave in Yucatan- that much more spectacular.
As expected, the mitochondrial DNA taken of the skeleton of a teenage girl who lived 12,000 years ago shows clear Siberian ancestry. What is more surprising is that the skeleton’s facial features are different from modern Native Americans: narrow and more angular, with more protruding facial features. The reason for this difference is still a mystery, though scientists hypothesize that the change may have been to adapt to New World diet or environmental differences.
While certain species in the animal kingdom can do basic addition and subtraction, more complex math- such as determine if the sum of two values is greater than that of another value- is a more difficult concept for animals to grasp. Rhesus macaques, a kind of monkey that native to Southeast Asia, seem to be an exception. After being taught to identify 25 numbers- done through a combination of the Arabic numbers 0-9 and 15 letters- the monkeys were shown the sum of two values and another single value, with a reward of correspondingly larger drops of orange soda or apple juice if they chose the larger sum. By and large, the monkeys chose the larger sum over the single, lesser value.
Interestingly enough, the monkeys seemed to have a hard time differentiating between a sum and a single value when both were only one or two numbers apart. Scientists discovered that this is because the monkeys, when adding sums, looked at the first value in a problem more than the second one, adding only a fraction of the second value to the first to determine if the sum was larger than the opposing value. Scientists believe that these findings could help students who suffer from math-related learning disabilities.
The controversy over whether gluten-free diets have any benefit for individuals who are not suffering from celiac disease is once again in the headlines. Yet very few people even know what gluten is. This video by ASAP science very nicely describes the basic role of gluten in nutrition and explains how it relates to the medical problems associated with celiac disease.