Transmission of Genetic Information

Three major components in the transmission of genetic information are deoxyribonucleic acids (DNA), ribonucleic acids (RNA), and proteins. The genetic code expressed through DNA ultimately determines which proteins a cell will produce. Coiled and supercoiled DNA molecules contain numerous sequences of nucleotides that may be transcribed as RNAs and translated to many different proteins. DNA molecules also contain long sequences of nucleotides not coding for protein and whose purpose is not completely understood. A gene is a specific sequence of DNA that encodes a sequence of messenger 

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NUCLEOPROTEINS. Nucleoprotein conjugates have many roles in the storage and transmission of genetic information. Ribosomes are the sites of protein synthesis. Virus particles and even chromosomes are protein-nucleic acid complexes. 

DNA replication yields two DNA molecules identical to die original one, ensuring transmission of genetic information to daughter cells widi exceptional fidelity. 

Deoxyribonucleic acid (DNA) is a very important biopolymer with the function of storage and transmission of genetic information. In this reason the protection of structural integrity and functional activity of DNA is essential for the viability of living systems, as well as the effectiveness of laboratory DNA-technics. 

What are the facts of life One of the most striking is that all known living systems involve the same types of polymers, i.e., three varieties of homochiral biopolymers. That is, each variety is composed of unique molecular building blocks having the same three-dimensional handedness. Thus, with rare exceptions, the proteins found in cells are composed exclusively of the 1-enantiomers of 19 optically active amino acids (Fig. 11.1). Similarly, only D-ribose and 2-deoxy-D-ribose sugars are found in the nucleic acid polymers that make up the RNAs and DNAs, which are essential for protein synthesis in the cell and for the transmission of genetic information from one generation to the next. 

Furthermore, this specificity of base pairing is what permits the transmission of genetic information from one generation to another. When cell duplication occurs, the DNA double helix unwinds, and two new DNA strands are formed that are complementary to the original strands. Thus, each of the new cells contains one of the original DNA strands and one newly synthesized strand in its double helix. 

Theories for even earlier forms of mutateable transmission of genetic information have involved clay minerals. Montmorillonite clay particles have been demonstrated to catalyse the condensation of nucleotides and we discussed in Section 8.2.8 the Cairns Smith hypothesis of how crystal dislocations could transmit some form of genetic information. Most hypotheses about clays have yet to be demonstrated experimentally, however. 

The two major classes of nucleic acids are ribonucleic acids (RNA) and deoxyribonucleic acids (DNA). In a typical cell, DNA is found primarily in the nucleus, where it carries the permanent genetic code. The molecules of DNA are huge, with molecular weights up to 50 billion. When the cell divides, DNA replicates to form two copies for the daughter cells. DNA is relatively stable, providing a medium for transmission of genetic information from one generation to the next. 

Recently a field of science called Life Science has been developed and its further development as a synthetic science which is related to a wide range of scientific fields is expected in the future. The aim of life science is to investigate the structure and properties of biomolecules that govern life activity, to elucidate the mechanism of the reactions of biomolecules, and to utilize the aspects of biomolecules for reactions in vitro. There are a number of polymeric compounds in vivo, such as proteins, that are related directly to life phenomena and nucleic acids that control the transmission of genetic information. To understand the functionality of these biopdymers and to exploit useful functional materials, an investigation on Biologically Important Polymers should be based on polymer chenustry. 

In biological systems, proteins and nucleic acids perform two major roles metabolism and conversion of materials and the storage and transmission of genetic information. Proteins are synthesized according to programs written in DNA, while nucleic acid replication and repair both require protein functionality. Proteins and nucleic acids needs each other - they are interdependent. 

Life is also complex and the detailed chemistry of how the organic molecules which sustain and regulate life were formed is yet to be worked out. However, there was process in which simple molecules were synthesized to form complex polymers useful in the process of replication and the transmission of genetic information. Many believe that the nucleic add RNA was a precursor to the modem DNA and that life first developed in an RNA world. In addition the relevant energy sources were harnessed to facilitate life. Now these come mostly from sunlight, but in the early Earth they were probably chemical. 

Fig. 8.2 The activities of regulatory npcRNAs affect all stages of transmission of genetic information from DNA to proteins.

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