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
Single-stranded DNA and RNA origami go live
15.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard
New antbird species discovered in Peru by LSU ornithologists
15.12.2017 | Louisiana State University
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences