![]() The importance of DNA became clear in 1953 thanks to the work of James Watson*, Francis Crick, Maurice Wilkins and Rosalind Franklin. Instead, they argued that proteins were more likely to carry out this vital function because of their greater complexity and wider variety of forms. Most thought that DNA was too simple a molecule to play such a critical role. But nearly a century passed from that discovery until researchers unraveled the structure of the DNA molecule and realized its central importance to biology.įor many years, scientists debated which molecule carried life's biological instructions. The Swiss biochemist Frederich Miescher first observed DNA in the late 1800s. This occurs because only egg cells, and not sperm cells, keep their mitochondria during fertilization. However, organisms inherit all of their mitochondrial DNA from the female parent. In sexual reproduction, organisms inherit half of their nuclear DNA from the male parent and half from the female parent. Mitochondria generate the energy the cell needs to function properly. An organism's complete set of nuclear DNA is called its genome.īesides the DNA located in the nucleus, humans and other complex organisms also have a small amount of DNA in cell structures known as mitochondria. ![]() Researchers refer to DNA found in the cell's nucleus as nuclear DNA. But during cell division, DNA is in its compact chromosome form to enable transfer to new cells. At other times in the cell cycle, DNA also unwinds so that its instructions can be used to make proteins and for other biological processes. This packaged form of the DNA is called a chromosome.ĭuring DNA replication, DNA unwinds so it can be copied. Because the cell is very small, and because organisms have many DNA molecules per cell, each DNA molecule must be tightly packaged. It is even possible that nascent life forms could have been transferred between worlds such as Earth and Mars through a process known as panspermia, in which organisms are able to survive by traveling through space on meteorites ejected by impacts with other space rocks.In organisms called eukaryotes, DNA is found inside a special area of the cell called the nucleus. Thus, the discovery provides the basis for confirming the theory that the seeds of life on our planet were sown by meteorites in the early stages of the formation of the Earth. Other key ingredients for life were also found in them: proteins, nitrogen, water and other organic compounds. The team achieved this breakout by analyzing samples of the Murchison, Murray and Tagish Lake meteorites that fell in Australia, Oklahoma and British Columbia, respectively. Journey of the “bricks of life” between the worlds “This study demonstrates that a variety of meteoric nitrogenous bases could have served as the building blocks of DNA and RNA in the early stages of the formation of the Earth,” says Yasuhiro Oba. Although uracil has been identified in meteorites before, the discovery of all three pyrimidines in space rocks sheds new light on the mysterious rarity of these nitrogenous bases in meteorites compared to purines adenine and guanine. In addition to finding the remaining compounds inside the DNA, Oba and his colleagues also found traces of another pyrimidine called uracil, which is used by RNA, a simpler sister DNA molecule, instead of thymine. Two recently discovered nitrogenous bases belong to a group called pyrimidines, while adenine and guanine belong to the purine category. This discovery is described in a published article in the journal Nature Communications. Now scientists led by Yasuhiro Oba, a professor at Hokkaido University, have finally discovered traces of cytosine and thymine in three carbon-rich meteorites. The researchers guessed that these compounds could also exist in the primary interstellar dust that gave rise to our Solar System about 4.6 billion years ago, but it was not possible to prove this in practice for a long time. But the presence of cytosine and thymine in extraterrestrial objects remained elusive. Adenine and guanine were discovered in meteorites about 50 years ago. Their combinations are arranged in a certain sequence, in which the source code for life on Earth, including humanity, is stored. The key ingredients for the origin of life were discovered in meteoritesĭNA is a helical structure consisting of so-called “nucleobases” - the compounds of adenine, guanine, cytosine and thymine. This discovery suggests that the key ingredients of life could be brought to Earth by ancient extraterrestrial objects. For the first time, all four main components of DNA – the basis of living beings – were discovered in meteorites from space.
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