Nucleic acids Human Genome

Viruses are small infectious agents composed of a nucleic acid genome (DNA or RNA) encased by structural proteins and in some cases a lipid envelope. They are the causative agents of a number of human infectious diseases, the most important for public health today being acquired immunodeficiency syndrome (AIDS), hepatitis, influenza, measles, and vituses causing diarrhoea (e.g., rotavirus). In addition, certain viruses contribute to the development of cancer. Antiviral drugs inhibit viral replication by specifically targeting viral enzymes or functions and are used to treat specific virus-associated diseases. 

Human genome Nucleic acid sequences representing endogenous retroviruses are com-... 

Z. Zhang, and M. Gerstein, Patterns of nucleotide substitution, insertion and deletion in the human genome inferred from pseudogenes. Nucleic Acids Res. 31, 5338-5348 (2003). 

Theoretically, mutated or nonfunctional genes could be excised and replaced, and new genes with desired functions could be permanently inserted into the genome. Stable integration of an antisense DNA might also be desirable in some circumstances. Because of the technical difficulties associated with the delivery of nucleic acid-based products selectively to specific target cells in vivo, more experimental information is available for ex vivo human gene therapy. 

Less than one-third of human genomic DNA consists of genes. Much of the remainder consists of repeated sequences of various types. Nucleic acid parasites known as transposons account for about half of the human genome. 

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