03-Nucleic Acids

03-Nucleic Acids - Nucleic Acids Nucleic Acids: DNA and...

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Nucleic Acids Nucleic Acids: DNA and RNA. Used as carriers of genetic information. Macromolecules consist of large number of linked nucleotides, each composed of a sugar, a phosphate, and a base. Genetic information is stored in the sequence of bases on a nucleic acid chain. The bases form specific pairs stabilized by H-bonds. The pairing provides a mechanism for copying the genetic information from an existing nucleic acid chain to form a new chain. DNA is replicated by DNA polymerase enzyme with error rate of 1 in 100 million. Gene expression: DNA is transcribed to RNA, which is translated into proteins. Transcription, translation. mRNA (messenger): template for protein synthesis. tRNA (transfer): selectively delivers amino acids in protein synthesis. rRNA (ribosomal): core of catalyzing protein synthesis. Codon: a sequence of three bases that specifies an amino acid. Introns: transcribed segment of nucleic acid that is excised from the final mRNA. Exons: transcribed segment of nucleic acid that is included in the final mRNA.
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DNA and RNA Nucleic acids (DNA and RNA) are linear polymers built from nucleotides, each composed of a sugar, a phosphate, and a base. DNA (deoxyribonucleic acid): the sugar is deoxyribose, without 2’-hydroxyl. RNA (ribonucleic acid): the sugar is ribose, with 2’-hydroxyl. The sugars are linked to one another by phosphodiester bonds. The 3’-hydroxyl group of one nucleotide is esterified to a phosphate group, which is joined to the 5’-hydroxyl of the adjacent sugar. The negative charge on the backbone repels nucleophilic species such as hydroxide ion making these ester linkages more resistant to hydrolysis. The lack of the 2’-hydroxyl group in DNA makes it more stable than RNA. The backbone is constant with varying bases.
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DNA and RNA The lack of the 2’-hydroxyl group in DNA makes it more stable than RNA. Base O OH O O P RO O O Base O O O O P O O
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Nucleic Acid Bases Purine bases: adenine (A), guanine (G). Linked to sugar C-1 through N-9 of purine ring. Pyrimidine bases: cytosine (C), thymine (T, DNA), uracil (U, RNA) Linked to sugar C-1 through N-1 of pyrimidine ring.
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Nucleosides and Nucleotides Nucleo s ide s: unit consisting of a base bonded to a sugar. The four nucleoside units in RNA: adenosine, guanosine, cytidine, and uridine. The four nucleoside units in DNA: deoxyadenosine, deoxyguanosine, deoxycytidine, thymidine. Base is attached to the C-1’ of the sugar through purine N-9 or pyrimindine N-1. The configuration of the N -glycoside linkage is a β . Nucleotides: nucleoside joined to 1 phosphate group by an ester linkage. The most common esterification site is at the C-5’ of the sugar: a
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This note was uploaded on 11/10/2010 for the course CHE Biochem taught by Professor Disney during the Spring '10 term at SUNY Buffalo.

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03-Nucleic Acids - Nucleic Acids Nucleic Acids: DNA and...

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