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Abstract
In this essay, we provided an introduction discussing the basic concepts in molecular cell biology. It is necessary to understand this rapidly advancing field in order to appreciate fully modern oncology including new methods of diagnosis and treatment. Among the basic concepts discussed was the genome which refers to the complete DNA sequence of an organism, which is enclosed in the nucleus of a cell. In molecular biology the basic units of DNA are base pairs and the genome may contain some three billion base pairs. In practice, one frequently deals in kilo- and megabases. Another important concept is the gene which is a distinct segment of the DNA forming a chromosome that has the appropriate DNA sequences promoting transcription to mRNA, and coding sequences to be transcribed and subsequently translated into a single polypeptide. “Head and neck cancer” is a collective term defined on anatomical-topographical basis to describe the malignant tumors of the upper aerodigestive tract. This anatomical region includes the oral cavity, pharynx and larynx. The study of genetic susceptibilities to epidemiological carcinogens can improve the accuracy of estimates for association from carcinogen exposure. For example, tobacco smoke contains numerous carcinogens that cause DNA damage. Oropharyngeal epithelium can metabolically activate tobacco smoke carcinogens, which cause DNA damage. The strategies that tumors have evolved for subversion of the host immune system are many; these are generally successful strategies that are seen in a majority of tumor cases and that have profound implications not only for immune-mediated therapies but also for patient survival . The aim of this essay is to study the molecular changes in malignant tumors of head and neck that enable us to understand the events that are occurring at the cellular and subcellular levels and their association with oncogenesis which help to evaluate tumor behavior . Key words : DNA Deoxyribonucleic Acid . APM Antigen Processing Machinery mRNA Messenger Ribonucleic Acid .