When did the double helix DNA invente?
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The DNA Double Helix is one of the greatest scientific discoveries of all time. First described by James Watson and Francis Crick in 1953, DNA is the famous molecule of genetics that establishes each organism's physical characteristics. It wasn't until mid-2001, that the Human Genome Project and Celera Genomics jointly presented the true nature and complexity of the digital code inherent in DNA. We now understand that there are approximately 35,000 genes in each human DNA molecule, comprised of chemical bases arranged in approximately 3 billion precise sequences. Even the DNA molecule for the single-celled bacterium, E. coli, contains enough information to fill all the books in any of the world's largest libraries.
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DNA has the form of a double helix. It is also anti parallel.
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Discovery of the DNA structure.\n\nThe discovery of the DNA structure was the start of a new era in biology, leading, over the next two decades, to the cracking of the genetic code and the realization that DNA directs the synthesis of proteins. There were technical advances too, such as DNA sequencing, genetic engineering, and gene cloning. More recently, the complete sequences of many organisms have been solved - including the human genome in June 2000. The next 50 years of the DNA story will be all about realizing the practical benefits of Crick and Watson's discovery for humanity - in industry, medicine, food and agriculture.
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Although sometimes called "the molecule of heredity", DNA macromolecules as people typically think of them are not single molecules. Rather, they are pairs of molecules, which entwine like vines to form a double helix (see the illustration at the right).\n\nEach vine-like molecule is a strand of DNA: a chemically linked chain of nucleotides, each of which consists of a sugar (deoxyribose), a phosphate and one of five kinds of nucleobases ("bases"). Because DNA strands are composed of these nucleotide subunits, they are polymers.\n\nThe diversity of the bases means that there are five kinds of nucleotides, which are commonly referred to by the identity of their bases. These are adenine (A), thymine (T), uracil (U), cytosine (C), and guanine (G). U is rarely found in DNA except as a result of chemical degradation of C, but in some viruses, notably PBS1 phage DNA, U completely replaces the usual T in its DNA. Similarly, RNA usually contains U in place of T, but in certain RNAs such as transfer RNA, T is always found in some positions. Thus, the only true difference between DNA and RNA is the sugar, 2-deoxyribose in DNA and ribose in RNA.\n\nIn a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect and pi stacking. Specificity of which strands stay associated is determined by complementary pairing. Each base forms hydrogen bonds readily to only one other -- A to T and C to G -- so that the identity of the base on one strand dictates the strength of the association; the more complementary bases exist, the stronger and longer-lasting the association.\n\nThe cell's machinery is capable of melting or disassociating a DNA double helix, and using each DNA strand as a template for synthesizing a new strand which is nearly identical to the previous strand. Errors that occur in the synthesis are known as mutations. The process known as PCR (polymerase chain reaction) mimics this process in vitro in a nonliving system.\n\nBecause pairing causes the nucleotide bases to face the helical axis, the sugar and phosphate groups of the nucleotides run along the outside; the two chains they form are sometimes called the "backbones" of the helix. In fact, it is chemical bonds between the phosphates and the sugars that link one nucleotide to the next in the DNA strand.
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Science estimates that the first DNA forms of life were present on Earth around 3.5 billion years ago.
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Darwin did just about everything, much more than just evolution. He also discovered how an atolls were formed. Gregor Mendel for genetics, Watsin and Crick for DNA, Coriolis, for the coriolis effect. If you really need to know this now, why not look it up yourself?
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make a model of DNA with wires and thermocole balls
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Charles Darwin, the discoverer of evolution; Watson and Crick, the discoverers of DNA
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well let me think...ITS A DOUBLE HELIX!!!!!!!!!!!!\nDOUBLE          DOUBLE               DOUBLE
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well people at that time were obsessed with finding what the key to life was and Watson and Crick took the data from other scientists who were studying the same subject, they analyzed the data from Cargraff's studies about how A only pairs with T and C with G. They also looked at x-rays made by Rosiland Franklin. They also looked at data produced by Maurice Wilkins(read more in source sites)So basicly watson and crick took other peoples data and compiled it to produce the double helix model, since the other people were not working with each other each had a piece of the puzzle but could not completely decipher DNA.
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For the past 50 years, scientists have attacked the question of how life began in a pincer movement. Some approach it from the present, moving backward in time from life today to its simpler ancestors. Others march forward from the formation of Earth 4.55 billion years ago, exploring how lifeless chemicals might have become organized into living matter.\n\nWorking backward, paleontologists have found fossils of microbes dating back at least 3.4 billion years. Chemical analysis of even older rocks suggests that photosynthetic organisms were already well established on Earth by 3.7 billion years ago. Researchers suspect that the organisms that left these traces shared the same basic traits found in all life today. All free-living organisms encode genetic information in DNA and catalyze chemical reactions using proteins. Because DNA and proteins depend so intimately on each other for their survival, it's hard to imagine one of them having evolved first. But it's just as implausible for them to have emerged simultaneously out of a prebiotic soup.\n\nExperiments now suggest that earlier forms of life could have been based on a third kind of molecule found in today's organisms: RNA. Once considered nothing more than a cellular courier, RNA turns out to be astonishingly versatile, not only encoding genetic information but also acting like a protein. Some RNA molecules switch genes on and off, for example, whereas others bind to proteins and other molecules. Laboratory experiments suggest that RNA could have replicated itself and carried out the other functions required to keep a primitive cell alive.\n\nOnly after life passed through this "RNA world," many scientists now agree, did it take on a more familiar cast. Proteins are thousands of times more efficient as a catalyst than RNA is, and so once they emerged they would have been favored by natural selection. Likewise, genetic information can be replicated from DNA with far fewer errors than it can from RNA.\n\nOther scientists have focused their efforts on figuring out how the lifeless chemistry of a prebiotic Earth could have given rise to an RNA world. In 1953, working at the University of Chicago, Stanley Miller and Harold Urey demonstrated that experiments could shed light on this question. They ran an electric current through a mix of ammonia, methane, and other gases believed at the time to have been present on early Earth. They found that they could produce amino acids and other important building blocks of life.
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The nucleolus suborganelle was originally discovered in eels by the Italian scientist Felice Fontana in 1774. He was able to see the large, darkly stained nucleolus under a simple light microscope. However, its function wasn't discovered until two centuries later.
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Each half of the double-helix sort-of "unzips" during replication.  Since each of the bases is kind of like a jigsaw-puzzle piece, the two strands can then wind back up, if supplied with the appropriate free bases, to form two identical copies of the original DNA strand.\n\nNeat, huh?
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The following wikipedia link talks about the DNA model watson and crick proposed. \n\nYou will also find that each of the scientists you listed above is mentioned in the article, and hyperlinks will take you to webpages with short biographies on their lives and their work.\n\n\nhttp://en.wikipedia.org/wiki/DNA#Watson_and_Crick.27s_model
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Waldeyer discovered chromosome\nHans krebs propounded kreb's cycle\nAnton van leewenhoek invented simple microscope\nWagner discovered nucleolus\nRobert Brown discovered nucleus\ncell theory propounded by  Schleiden(botanist)&Schwann(zoologist)
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Yeah, well if you don't like your theology that way we'll return to the science. Helical structures recur at many levels in the structure of macromolecules: DNA is a right handed helix, and much of protein structure consists of alpha helices. Both B-DNA's and the alpha helix twist is right-handed, and this is dictated by the sterics of the structure. However, the components of DNA are difficult to make in a "primordial soup" model, and so it probably wasn't important in the creation of life. Most models favour an "RNA-world" - since RNA can be both a catalyst and a store of information. RNA forms helices in stem-loops which again tend to be right handed, but the structure is much looser and more variable than in DNA. Hence I'd say helicity isn't really that important. A more interesting question is the origin of the universal chirality of biolical amino acids...
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Watson and Crick discovered it while researching "genetic material." For further information, check this site.