Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Selfing DNA prevents genomes from mixing

11.10.2002


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.


The chromatin diminution never takes place in cells of humans and most animals, but they isolate the selfing DNA in another way ? by placing it in a position unreachable for most enzymes and thus making it functionally cut off. Each species has a unique structure and packing of the selfing DNA. In other words, indirect ways of a physical separation of some part of genome are known for many organisms.

Thus, a certain part of a genome with a particular size and structure serves for the genetic isolation of species. Therefore the selfing or junk DNA is not a piece of garbage, but a vital component. If one mechanism eliminates it, another mechanism should restore it while a species still exists. The scientists expect to understand more, if they will manage to reveal the molecular organization of the selfing DNA. The most suitable material for this study is DNA lost from cells as a result of the diminution.

Natalia Reznik | alfa

More articles from Life Sciences:

nachricht Meadows beat out shrubs when it comes to storing carbon
23.11.2017 | Norwegian University of Science and Technology

nachricht Migrating Cells: Folds in the cell membrane supply material for necessary blebs
23.11.2017 | Westfälische Wilhelms-Universität Münster

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New proton record: Researchers measure magnetic moment with greatest possible precision

High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons

The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Lightning, with a chance of antimatter

24.11.2017 | Earth Sciences

A huge hydrogen generator at the Earth's core-mantle boundary

24.11.2017 | Earth Sciences

Scientists find why CP El Niño is harder to predict than EP El Niño

24.11.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>