![]() The chemistry of the phosphate groups forms another important part of the DNA structure, joining together the ribose sugars and bases to form a polymer with phosphodiester bonds. Guanine binds to Cytosine via 3 hydrogen bonds, as shown below, whereas Adenine binds to Thymine via 2 hydrogen bonds. These bases match up in complementary pairs due to the number of hydrogen bonds and relative sizes of the bases. These hydrogen bonds form between the amino groups on one base and the amino or carbonyl groups on the adjacent nitrogenous base. ![]() The nitrogenous bases of one strand in the double-stranded structure form hydrogen bonds to the other strand to form a double helix. As a polymer, DNA is made up of nucleotide monomers which each contain a nitrogenous base, ribose sugar, and phosphate group. ![]() The table below summarizes the possibilities.DNA is a nucleic acid that contains monomer nucleotide units formed into a polymer and is held in a double helix structure by hydrogen bonding between nitrogenous bases of the two antiparallel strands.ĭNA contains a large range of important chemical concepts. The other oxygens in the backbone can only act as hydrogen bond acceptors. The oxygens at atom 7 can act as either a donor or an acceptor. Unlike the backbone of a protein, DNA backbone doesn't contain any nitrogen atoms, so hydrogen bonding must involve oxygen atoms. In RNA, atom 12 is the oxygen in the hydroxyl group, and the first base atom is 13. The first atom of the base in DNA is atom 12. Atom numbering continues normally from there, and no "virtual atoms" are involved. Since there's no next DNA segment, the oxygen at atom 9 is not attached to a phosphate group. Foldit still identifies atoms 1 through 4 as being present, and these "virtual atoms" can even be banded.įor the last DNA segment in a chain, numbering is more straightforward. The first atom visible is atom 5, a carbon attached to the deoxyribose ring. Atom 10 is a carbon (carbon 1'), which is where the actual DNA base is attached.įor the first DNA segment in a chain, the phosphate group is missing. Atom 9 is an oxygen which joins the phosphate group of the next DNA segment. Foldit considers one of the oxygen atoms of the phosphate to belong to the deoxyribose of the preceding segment, so only the oxygen atoms 2 through 4 are numbered.Ītom numbering continues with the dexoyribose group. Foldit starts numbering with the phosphorous in the phosphate group. For example, the C terminal of a chain has an extra backbone atom, so it's beta carbon, the first atom of the sidechain, is 6 instead of 5.įor DNA, the backbone atoms always have the same number, regardless position in the chain. In a protein, the number of atoms in a segment is different depending on its position in the chain. The rules for numbering atoms are different in DNA, however. Just as in a protein, Foldit can identify atom numbers in DNA. The statements below are based on the similarities between RNA and DNA. DNA has only been found in intro puzzles to date, which don't allow the use of the recipes used to verify RNA atom numbering. The hydroxyl group is what distinguishes RNA from DNA.Ĭaution: atom numbering for DNA has not been validated. In RNA, a hydroxyl group (oxygen and hydrogen) is attached to carbon 2'. The DNA base is attached to carbon 1' of the deoxyribose. The carbon atoms are referred to as 1', 2', 3' and 4'. The sugar group in the DNA backbone is always a form of deoxyribose, a pentagonal ring consisting of an oxygen atom and four carbon atoms. Each segment of DNA or RNA is linked to the next by a phosphate. A phosphate group consists of a phosphorous atom bound to four oxygen atoms. This is why "RNA" stands for "ribonucleic acid", and "DNA" stands for "deoxyribonucleic acid".īoth DNA and RNA backbone consists of alternating groups phosphates and sugars. The difference is that RNA backbone contains the sugar ribose, while DNA backbone contains the sugar deoxyribose. The blue numbers 1' to 4' refer to the carbons in the in deoxyribose ring.ĭNA backbone is more complicated than the backbone of the amino acids in a protein.ĭNA backbone is highly similar to RNA backbone.
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