![]() DNA consists of A, T, G and C and the absence of U, while RNA consists of A, U, G and C and the absence of Tģ. DNA is a double-stranded molecule while RNA is a single-stranded molecule. It provides the site where polypeptide chains are assembled.ġ. Linear, but forms three-looped structures as shown in the diagram.įig 2.17: Structure of the tRNA molecule įunction - transportation of amino acids to the site of protein synthesis. Transports genetic information from nucleoplasm to the site of protein synthesis (ribosome) through nucleopores.Copies the genetic information stored in DNA molecules as a sequence of nitrogenous bases.Messenger RNA is a linear molecule and is the least abundant type of RNA in cells comparatively. There are three types of RNA present in cells, Adenine binds with Uracil with two hydrogen bonds and Guanine binds with Cytosine with three hydrogen bonds. Complementary base pairing facilitates three-dimensional shapes essential for their functioning. Complementary base pairing between two RNA molecules or within the same molecule may occur in some. This is normally a single-stranded nucleic acid composed of ribonucleotides containing bases, Uracil (U), Cytosine (C ), Guanine (G), and Adenine (A). Store the genetic information for protein synthesis.Store and transmit genetic information from one generation to the next generation.In this original double helical structure, one complete turn consists of ten base pairs as shown in the diagram.įig2.16: The structure of the DNA and RNA molecules These pairs are known as complementary base pairs. Hence two chains (strands) are said to be complementary to each other. Base pair-ruleĪlways a purine base, pairs with a specific pyrimidine base The two strands are held together by hydrogen bonds between the paired nitrogen bases. The sugar-phosphate backbones are on the outside of the helix, and the nitrogenous bases are paired in the interior of the helix. The two sugar-phosphate backbones run in opposite directions from each other, and the arrangement is referred to as anti-parallel. Structure of DNA molecule (Watson and Crick model)ĭNA molecules have two anti-parallel polynucleotide chains that spiral around an imaginary axis, forming a double helix. DNA contains Adenine, Thymine, Guanine and Cytosine and RNA contains Adenine, Guanine, Cytosine and Uracil. If the pentose sugar is ribose, then the nucleic acid is RNA. If the sugar molecule in the nucleotide is deoxyribose, the nucleic acid is (DNA). There are two kinds of nucleic acids depending on the type of sugar molecules involved. Nucleic acids are linear polymers of nucleotides. These bonds result in a backbone with a repeating pattern of sugar-phosphate units. Millions of nucleotides are joined by a phospho-di-ester bond to form polynucleotide chains by condensation between the –OH group of the phosphate of one nucleotide with the –OH attached to the 3rd carbon of pentose sugar of the other. It gives the nucleic acids an acidic nature. Bases are commonly represented by letters A, G, T, U and C respectively. In pyrimidines, there are three types, Thyamine, Uracil and Cytosine. In purines, there are two types namely Adenine, Guanine. Pyrimidines- smaller in size with a single ring There are two major groups of nitrogenous bases:ġ. Pentose sugars are two types namely Deoxy ribose and ribose (in deoxyribose one oxygen atom is less than in ribose) Nitrogenous bases Nucleotides have 3 components namely pentose sugar, a nitrogenous base and a phosphate groupįig 2.15: Structure of nucleotides Ī nucleotide without a phosphate group is called a nucleoside. There are two types of Nucleic acids: DNA (Deoxyribonucleic acids) and RNA (Ribonucleic acids). Nucleic acids are macromolecules and biopolymers. Nucleic acids are Polymers that exist as polynucleotides made up of monomers called nucleotides.
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