Genomes of multicellular organisms are one of the greatest mysteries of biology. The more is discovered about them, the more questions are to be answered. One of such questions is connected with the size of a genome. As is known since the middle of the 20th century, the level of organization of an organism does not depend on the genome size, i.e., on the amount of DNA in the nucleus of a cell. Sometimes, a primitive organism contains much more DNA than a mammal. For example, the genome of certain amoebas is 200 times as large as that of humans. The nature of this phenomenon has been understood very recently. The most part of DNA does not contain any of protein-coding genes. Because of its unclear function, it is called the selfing or junk DNA, which is somewhat abusive. Its share in genomes of some species riches 95% (in human genome, its content is 75%). The selfing DNA can hardly serve as a material for evolution: it is so unstable that has no time to develop into a functional structure. However, as long as each species has its specific junk DNA, it must serve for something.
Different scientists tried to find an explanation for the biological purpose of the selfing DNA. About fifteen hypotheses were offered, and most of them turned to be invalid. In Russia, this problem has been studied for many years by doctor of biological sciences Aleksei Akifyev and his colleagues. The scientists believe that an actual function of the selfing DNA stands behind a phenomenon known for already 100 years and called the chromatin diminution. This is a key term in this context, let us remember it. The chromatin diminution is the elimination of an inactive chromatin from a genome. Some multicellular animals, such as ascarids and small crustaceans Cyclopoida, lose an important part of their chromosomal DNA at the early stages of embryogenesis. The diminution normally takes place in cells that are to build the body and never occurs in developmental precursors of germ cells. The latter still have all their selfing DNA. Apparently, these are the cells, in which the selfing DNA is functionally significant. The scientists have revealed that the selfing DNA prevents the confusion of closely related species.
Aleksei Akifyev and his colleagues have studied the genetic isolation mechanism using near species of crustaceans Cyclopoida as an example. The chromatin diminution is characteristic of one species and never occurs with the other. The researchers suggest that the DNA elimination is performed by certain enzymes that cut the genome at the right time and in the right place and are contained in the cytoplasm of an ovum. If a sperm cell of one species enters an ovum of another species, then the embryo dies either because of a failure to perform a necessary diminution or because of an unreasonable elimination of vital chromosomes by aforementioned enzymes.
Natalia Reznik | alfa
A novel socio-ecological approach helps identifying suitable wolf habitats
17.02.2017 | Universität Zürich
New, ultra-flexible probes form reliable, scar-free integration with the brain
16.02.2017 | University of Texas at Austin
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
20.02.2017 | Materials Sciences
20.02.2017 | Health and Medicine
20.02.2017 | Health and Medicine