Primary structure, of nucleic acids

The sequence or order of the nucleotides defines the primary structure of DNA and RNA. The nucleotides of the polymer are linked by phosphodiester bonds 

Each nucleic acid has its own unique sequence of bases, which is known as its primary structure. It is this sequence of bases that carries the genetic information from one cell to the next. In any nucleic acid, the sugar at the one end has an unreacted or free 5 -phosphate terminal end, and the sugar at the other end has a free 3 -hydroxyl group. 

Draw the condensed structural formula for the RNA dinucleotide formed by two cytidine-5 -monophosphates. 

The dinucleotide is drawn by connecting the 3 -hydroxyl group on the first cytidine-5 -monophosphate with the 5 -phosphate group on the second. 

In the dinucleotide of cytidine shown in the solution to Sample Problem 17.2, identify the free 5 -phosphate gronp and the free 3 -hydroxyl group. 

In the primary stmcture of nucleic acids, each sugar in a sugar-phosphate backbone is attached to a base. 

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In contrast, RNA occurs in multiple copies and various forms (Table 11.2). Cells contain up to eight times as much RNA as DNA. RNA has a number of important biological functions, and on this basis, RNA molecules are categorized into several major types messenger RNA, ribosomal RNA, and transfer RNA. Eukaryotic cells contain an additional type, small nuclear RNA (snRNA). With these basic definitions in mind, let s now briefly consider the chemical and structural nature of DNA and the various RNAs. Chapter 12 elaborates on methods to determine the primary structure of nucleic acids by sequencing methods and discusses the secondary and tertiary structures of DNA and RNA. Part rV, Information Transfer, includes a detailed treatment of the dynamic role of nucleic acids in the molecular biology of the cell. 

The sequence of nucleotides in a nucleic acid is defined as the primary structure of nucleic acid. 

The primary structure of nucleic acids refers to the sequence in which the four nitrogen bases (A, G, C and T in DNA and A, G, C and U) in RNA are attached to sugar phosphate backbone of the nucleotide chain. 

In DNA the sugar molecule in the nucleotide is 2-deoxyribose, and in RNA it is ribose. The amine bases in DNA are adenine, thymine, cytosine, and guanine, symbolized by A, T, C, and G, respectively. RNA contains adenine, cytosine, and guanine, but thymine is replaced by the based uracil (Figure 16.16). The primary structure of nucleic acids is given by the sequence of the amine side chains starting from the phosphate end of the nucleotide. For example, a DNA sequence may be -T-A-A-G-C-T. 

What are the two most important discoveries that enabled biochemists to start determining the primary structure of nucleic acid polymers ... 

The linear sequence of nucleotides linked by phosphodiester bonds constitutes the primary structure of nucleic acids. Like polypeptides, polynucleotides can twist and fold Into three-dimensional conformations stabilized by noncovalent bonds. Although the primary structures of DNA and RNA are generally similar, their three-dimensional conformations are quite different. These structural differences are critical to the different functions of the two types of nucleic acids. 

In Chapter 4, we identified four levels of structure—primary, secondary, tertiary, and quaternary—in proteins. Nucleic acids can be viewed in the same way. The primary structure of nucleic acids is the order of bases in the polynucleotide sequence, and the secondary structure is the three-dimensional conformation of the backbone. The tertiary structure is specifically the supercoiling of the molecule. 

The primary structure of nucleic acids is the order of bases. The secondary structure is the three-dimensional conformation of the backbone. The tertiary structure is the supercoifing of the molecule. 

The sequence of bases is a very important feature of the primary structure of nucleic acids, because the sequence is the genetic information that ultimately leads to the sequence of RNA and protein. 

Hydrolysis of nucleoproteins separates the acids from the proteins. Further hydrolysis yields the components of nucleic acids, namely sugars, bases, and phosphoric acid. The nucleic acids differ from each other, depending upon the source, in chain lengths, sequences, and distributions of bases. As in the proteins, the primary structure of nucleic acids is determined by partial and sequential hydrolysis. 

Like proteins, nucleic acids have different modes of structure. Nucleotide sequence and covalent structure form the primary structure of nucleic acids. When nucleotides form regular and stable structures, it is referred as secondary structure. The ternary structure is considered as the folding of large chromosomes within the chromatin. 

Primary structure of nucleic acids The sequence of bases along the pentose-phosphodiester backbone of a DNA or RNA molecule, read from the 5 end to the 3 end. 

The essential foundation for these discoveries has been the knowledge of the primary structure of nucleic acids and the development of methods for their synthesis. 

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