Deoxyribonucleic acid complementary strands

Gene expression involves a few distinct and well-regulated steps. The first major step of gene expression involves transcription of a messenger RNA (mRNA) which is a RNA sequence complementary to the anti-sense deoxyribonucleic acid (DNA) strands, or, in other words, identical in sequence to the DNA sense strand, composing the gene. 

Figure 7.5 Example of a chimeric oligonucleic acid and its modification. Chimeric RNA-DNA hybrids are used for correction of point mutations in target genes. One strand of this oligonucleic acid is composed of O-methyl-RNA (outline) with an interruption of 5 bases of deoxyribonucleic acid. X and Y are target residues for correction. In the complementary strand, there is a DNA nick, and T residues loop both ends. 3 -exonuclease and FEN-1 may act on the nick, PARP-1 possibly binds to and is activated by the nick, resulting in activation of damage response pathways. In the modified version, the 3 end is replaced by ribonucleic acids. The 5 end is extended, and the flipped back RNA tail is added. Thus, the nick is expected to be resistant to 3 -exonuclease and FEN-1. In addition, PARP-1 may not be activated by such a nick.

As much of the terminology used in molecular biology may be unfamiliar to some readers, it is appropriate to define some of the vocabulary and this is given in an appendix to this chapter. There are two types of nucleic acids, the ribonucleic acids (RNA) and the deoxyribonucleic acids (DNA). Genetic information is carried in the linear sequence of nucleotides in DNA. Each molecule of DNA contains two complementary strands of deoxyribonucleotides which contain the purine bases, adenine and guanine and the pyrimidines, cytosine and thymine. RNA is single-stranded, being composed of a linear sequence of ribonucleotides the bases are the same as in DNA with the exception that thymine is replaced by the closely related base uracil. DNA replication occurs by the polymerisation of a new complementary strand on to each of the old strands. 

During the past half a century, fundamental scientific discoveries have been aided by the symmetry concept. They have played a role in the continuing quest for establishing the system of fundamental particles [7], It is an area where symmetry breaking has played as important a role as symmetry. The most important biological discovery since Darwin s theory of evolution was the double helical structure of the matter of heredity, DNA, by Francis Crick and James D. Watson (Figure 1-2) [8], In addition to the translational symmetry of helices (see, Chapter 8), the molecular structure of deoxyribonucleic acid as a whole has C2 rotational symmetry in accordance with the complementary nature of its two antiparallel strands [9], The discovery of the double helix was as much a chemical discovery as it was important for biology, and lately, for the biomedical sciences. 

Deoxyribonucleic acid (DNA) a huge nucleotide polymer having a double-helical structure with complementary bases on the two strands. Its major functions are protein synthesis and the storage and transport of genetic information. (22.6) Desalination the removal of dissolved salts from an aqueous solution. (17.6)... 

Deoxyribonucleic acid, d(C-A-T-C-A-C-G-T-G-A-G-A-T-A-A-G-A-G-C-C-G-C-C-A), double-stranded complementary 950b, 4249... 

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