Cancer 2
Cancer 2Introduction to Cancer
The individual unruly cell that has escaped the normal regulatory control mechanisms is the basic unit of cancer.
Inside the nucleus is a substance called DNA, which contains genetic information for the body, organized in units called genes. These genes contain the complete plans for the body. They determine weather you have a blue or a green eye, weather you will have two or four legs, etc. They send out information that tells the cell what chemicals to make, as well as how much and when to make them.
In nucleus, genes are joined together, like beads on a chain, into structures called chromosomes. A normal human body cell has 46 chromosomes, which contain an average of several thousand genes each. During certain phases of the cell's life cycle, the chromosomes are stretched out into long, thin strands, and they are tangled together into a network called chromatin. In addition to genes, chromosomes contain proteins, some of which cover the genes that are not "turned on" at the particular time.
The original genetic information, stored in a coded form DNA, is carried out of the nucleus by RNA and then translated into proteins by ribosomes. 70% of oncogenes are located in the weak points of the chromosomes-hereditary regions where the DNA molecule may break or its portions may be rearranged into new combinations. Actually most of the times, the nucleus and the DNA are constantly exposed to substances that may alter the genes. But these alterations are almost always prepared by intricate mechanism with the function of preventing havoc in the cell. But if these changes persist in a given cell, that altered gene will breed true. Such damage to the chromosome may remove the oncogene from the influence of the genetic control mechanisms that normally govern its actions or an inactive oncogene may remove next to another gene that has an activating affect. This way the DNA in the cell is changed to activate the oncogenes. Instead of sending out the signals for normal growth and development, oncogenes carry instructions that cause cells to grow and divide more rapidly than normal cells - Researchers have found that when the cell membranes of two normal cells touch each other, both cells stop growing. Somehow each gives the other a signal that turns off the DNA that controls cell growth and division. Scientists call this exchange of signal contact inhibition. But when two cancer cells touch each other, somehow the stop signal is not given or is not received properly. The DNA is not turned off and the cancer cells continue to grow and divide. They pile up in an untidy heap, one upon another. They can even invade normal tissues. Normally there is something like glue between the cells that hold them together. Cancer cells give off, or secrete a certain chemical that dissolves this glue. The cancer cells can...
To view the complete essay, you be registered.