Messenger RNA copying

Messenger ribonucleic acid (mRNA)—Messenger RNA copy of a gene used to make a protein in a cell it is complementary to and will bind to the DNA gene. 

DNA chain (source. IDFL) The code is quite easy to read. The cells read it by scanning down a messenger RNA (copied from the DNA) and use ribosomes to build proteins based on the code that is read. Researchers read the code by stepping down one nucleotide at a time, clipping it off to identify it, thus determining the sequence of a DNA strand. Hundreds of different proteins are built in to interact with the information contained in the DNA. Their sequence is genetically determined and varies between different animal species. 

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. 

Messenger RNA (mRNA) serves to carry the information or message that is encoded in genes to the sites of protein synthesis in the cell, where this information is translated into a polypeptide sequence. Because mRNA molecules are transcribed copies of the protein-coding genetic units that comprise most of DNA, mRNA is said to be the DNA-like RNA. ... 

Reverse transcription is the copying of an RNA molecule back into its DNA complement. The enzymes that perform this function are called reverse transcriptases. Reverse transcription is used naturally by retroviruses to insert themselves into an organism s genome. Artificially induced reverse transcription is a useful technique for translating unstable messenger RNA (mRNA) molecules into stable cDNA. 

Virus messenger RNA In order for the new virus-specific proteins to be made from the virus genome, it is necessary for new virus-specific RNA molecules to be made. Exactly how the virus brings about new mRNA synthesis depends upon the type of virus, and especially upon whether its genetic material is RNA or DNA, and whether it is single-stranded or double-stranded. Which copy is read into mRNA depends upon the location of the appropriate promoter, since the promoter points the direction that the RNA polymerase will follow. In cells (uninfected with virus) all mRNA is made on the DNA template, but with RNA viruses the situation is obviously different. 

A primer is a very special sequence, which plays an important role in duplication, (i) In RNA, it is a short sequence that is paired with one strand of DNA and provides a free 3 -OH terminus at which a DNA polymerase starts synthesis of a deoxyribonucleotide chain, (ii) In DNA, it is another short sequence, which is complementary to a sequence of messenger RNA and allows reverse transcriptase to start copying the adjacent sequences of mRNA. (iii) In retroviruses, it is a cellular transfer RNA whose elongation initiates RNA-directed DNA synthesis by the DNA polymerase. 

The RNA molecules, ribosomal RNA (rRNA) and messenger RNA (mRNA) play key roles in the protein synthesis. The amount of RNA in individual cells or in a community may, therefore, be taken as an indicator of protein synthesis and, thus, microbial activity. The number of active cells can be detected by fluorescent in situ hybridization (FISH) (Amann et al. 1995). By this method, individual cells carrying high concentrations of rRNA, situated on ribosomes, are quantified by fluorescence microscopy. The amount of rRNA in a community can also be detected by Reverse Transcriptase Polymerase Chain Reaction (RT-PCR), where rRNA extracted from soil is detected by creating a DNA copy and separating by gel electrophoresis (Duineveld et al. 2001). 

The relationship between the DNA in the nucleus and proteins in the cytoplasm is not direct. The information in the DNA molecule is transmitted to the protein-synthesizing machinery of the cell via another informational nucleic acid, called messenger RNA (mRNA), which is synthesized by an enzyme called RNA polymerase. Although similar to DNA, mRNAs are single-stranded, and possess the base uracil instead of thymine and the sugar ribose rather than deoxyribose. These molecules act as short-lived copies of the genes being expressed. 

List of Abbreviations PCR, polymerase chain reaction RT-PCR, reverse transcription polymerase chain reaction DNA, deoxyribonucleic acid RNA, ribonucleic acid RNase, ribonuclease mRNA, messenger RNA GABAa, y-aminobutyric acid type A cRNA, copy RNA dNTPs, deoxy nucleoside triphosphates MMLV, Mouse Moloney murine leukemia vims RT, reverse transcriptase bp, base pair Tm, melting temperature DEPC, diethylpyrocarbonate OD, optical density mL, milliliter SA-PMPs, streptavidin paramagnetic particles dT, deoxy thymidine DTT, dithiothreitol DNase, deoxyribonuclease RNasin, ribonuclease inhibitor UV, ultraviolet TBE, Tris-borate, 1 mM EDTA EDTA, ethylenediaminetetraacetic acid Buffer RET, guanidium thiocyanate lysis buffer PBS, phosphate buffered saline NT2, Ntera 2 neural progenitor cells... 

List of Abbreviations BCIP, 5-bromo-4-chloro-3-indolyl phosphate, toluidine salt CCD, charged-coupled device CNS, central nervous system cDNA, copy or complimentary RNA cRNA, copy or complimentary RNA DNase, deoxyribonuclease FITC, fluorescein isothiocyanate mRNA, messenger RNA NBT, nitro blue tetrazolium choride PCR, polymerase chain reaction RNase, ribonclease... 

Transcription is the term used to describe the synthesis of RNA from a DNA template. Translation is the process by which information in RNA is used to synthesise a polypeptide chain. In a little more detail, the genetic information encoded in DNAis first transcribed into acomplementary copy of RNA (a primary RNA transcript) which is then processed to form messenger RNA (mRNA). This leaves the nucleus and is translated into a polypeptide in the cytosol. This then folds into a three-dimensional structure and may be further biochemically modified (post-transla-tional modification) to produce a protein (Figure 20.18). 

Messenger RNAs (mRNAs) carry copies of the genes that can be translated... 

The sequence of the bases contains coded information for the synthesis of proteins. These sequences are transcribed into an RNA copy of the sequence messenger RNA (mRNA). The mRNA is translated in the cytoplasm. The DNA also encodes structural RNAs, with functions in transcription of the DNA, processing of the transcripts and translation of the transcripts. The genetic code shown in Table 8.2.1 is simple, but efficient. At each nucleotide position, there are only four possibilities A,... 

This revolution in our understanding of the structure of DNA inevitably stimulated questions about its function. The double-helical structure itself clearly suggested how DNA might be copied so that the information it contains can be transmitted from one generation to the next. Clarification of how the information in DNA is converted into functional proteins came with the discovery of both messenger RNA and transfer RNA and with the deciphering of the genetic code. 

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