The chromosomes within our cells contain an enormous amount of information. It is estimated that humans have somewhere around 30,000 genes. Each geneA stretch of DNA that leads to the production of an RNA. The RNA is produced during the process of transcription. This RNA can be used to guide the formation of a protein via translation or can be used directly in the cell. codes for an RNAAlso: ribonucleic acid. RNA is a polymer comprised of the nucleotides A, C, G and U. RNA is the working form of our genetic information. RNA is produced via the process of transcription. Some RNA is used to help build ribosomes (rRNA) and some (mRNA) are used to guide the formation of proteins. Other forms of RNA are used to perform specialized functions in the nucleus. molecule that is either used directly or used as a guide for the formation of a proteinOne of the four basic types of biomolecule. Proteins are polymers made up of strings of amino acids. Proteins serve many functions in organisms including transport of molecules, structure, cell adhesion and as signaling molecules such as hormones. Many transcription factors, including p53 and Rb are proteins. such as the insulinA protein hormone secreted by the pancreas. Insulin controls glucose levels in the body by increasing uptake of glucose into cells of the body. Insulin also stimulates the formation of glycogen and alters fat and protein metabolism. shown earlier. Information in our cells generally flows in a predictable order from the storage form of the information (DNAAbbreviation for deoxyribonucleic acid. Composed of very long strings of nucleotides, which are abbreviated as A, C, G and T. DNA is the storage form of our genetic material. All of the instructions for the production of proteins are encoded in our DNA. ) through the working form (RNA) into the final product (protein). This pathway is used by all organisms and is diagrammed below.
As shown, DNA is used as a guide or template for the production of more DNA. This process, known as replicationThe process by which DNA is duplicated. DNA replication occurs during the S phase (synthesis) of the cell cycle. Many chemotherapy drugs act during DNA replication. Some are incorporated into the newly replicated DNA and cause problems. Others interfere with enzymes necessary for DNA replication. See topoisomerase., is addressed here.
The process in which particular sections of DNA (genes) are used to produce RNA is known as transcriptionThe production of an RNA molecule from a DNA template. An RNA copy of a gene is produced by an enzyme, RNA polymerase. The RNA produced can either be used directly in the cell or can be used to direct the production of a protein through the process of translation. Many of the genes that are altered in cancer cells have potent effects on the process of transcription. See transcription factor.. We will cover transcription in some detail because alterations in the transcription of certain genes are very important in the development of cancer.
The set of genes that are 'on' at any given time is critical. The variable environment in which we live means that different genes need to be 'on' at different times. For example, if a meal contains large amounts of lactose, a sugar found in milk, then our bodies respond by turning on (transcribing) the genes that lead to the production of enzymes that break down lactose. If a different sugar or nutrient is present, the correct genes need to be turned on to process it.
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