الفهرس 
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Abstract
SUMMARY AND CONCLUSIONS
The total set of genes in an organism is known as its genome, which may be stored on one or more chromosomes.
Structure of a gene :
A chromosome consists of a single, very long DNA helix on which thousands of genes are encoded. DNA consists of a chain made from four types of nucleotide subunits; adenines, cytosine, guanine, and thymine. A universal regulation region shared by all genes is known as the promoter, the ends of eukaryotic chromosomes are capped by long stretches of repetitive sequences called telomeres.
Gene expression :
There are two major steps separating a protein-coding gene from DNA molecule
- Transcription; The DNA on which the gene resides must be transcribed from DNA to messenger RNA(mRNA).
- Translation; it must be the translated from mRNA into protein.
DNA replication and molecular inheritance :
Making a duplicate copy of every gene in the genome, the copies are made by specialized enzymes known as DNA polymerases. Organisms inherit the characteristics of their parents because the cells of the off spring contain copies of the genes in their parents’ cells.
Mutation :
Rare, spontaneous alterations in the base sequence of a particular gene arise from a number of sources, such as errors in DNA replication and the aftermath of DNA damage.
Gene therapy :
Gene therapy is designed to introduce genetic material into cells to compensate for abnormal genes or to make a beneficial protein. The genetic material used for gene therapy include both natural and chimeric genes and also subgenomic DNA and RNA molecules.
Both viral and non-viral vectors are used to transfer genetic material to the inside of target cells.
Gene therapy for viral hepatitis :
Gene therapy for viral hepatitis is aimed to boost the patient immune response against viral antigen or make cells resistant to infection by blocking the viral life cycle.
1- Down regulation of viral gene expression :
Ribozymes, DNA ribonucleases, Antisense RNA and more recently vectors expressing small hairpin containing inhibitory RNAs (shRNA) are being tested for inhibiting the replication of hepatitis B and C.
2- Antiviral immunity :
Gene therapy can also be used to introduce prophylactic or therapeutic antiviral immunity.
3- Gene transfer of IFN-alpha to the liver :
Gene transfer of IFN-alpha to the liver using a long term expression vector could induce prolonged and continous IFN-alpha production by the proper diseased liver
4- Suicidal gene therapy fights hepatitis :
Remove the genetic code that allows the protein to recognize the human protease and replaced it with code specific to the hepatitis C protease. If a cell is infected, then the viral protease causes it to order its own death.