Gene expression

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 squeeze through the normal cells and spread through them. They form a growing lump of cancerous tissue called a tumor. Dozens of oncogenes have already been isolated and their protein products have been determined.

Some of these are enzymes, which cause biochemical changes in other protein molecules and their behavior. Others are DNA – binding proteins that may act directly on particular genes and turn them off. Still others have structures and activities very similar to growth hormones or the structures on the cell surface (receptors) that interact with them and give chemical instructions that tells the cell to grow. They cause cancer: some of these oncogenes give cells the ability to go on growing indefinitely; others affect the way cells interact with their neighbors.

When a cancer cell divides, each of its daughter cells receives a complete set of genes-including the activated oncogenes that prompt them to grow furiously, too. Soon a growing mass of cells forms, crowding out the normal body cells. This is cancer. Cancer cells do not stick to each other well, and may break away and be carried along in the blood stream or lymph channels. This way, they can settle in other parts of the body and begin to grow there too. This migration of cancer cells by the blood streamed lymph circulation is called metastasis.

This type of cancers are the deadliest, because even if the surgeon be able to remove the tumor completely, the small secondary tumors are still lurking in other parts of the body, and the treatments may not reach them. Cancer cells do not necessarily grow faster than normal cells, they continue to grow under conditions when normal cells would stop. They look different from normal cells. Therefore the more abnormal the cell appear, the more malignant the cancer. They can be identified by microscope. They are disorganized, abnormal, inconsistent in size and shape.

Cancer cells may invade the bloodstream and establish colonies far from the original site called metastasis. Types of Cancer 1. Carcinomas: Malignant growths attached to a part of the body’s lining (which includes the skin, the inside and outside of the body’s organs, the glands, the lungs, and the digestive tract. It comes from the Greek word meaning “crab”. A small carcinomas developing inside a person’s body may be there for several years before the person becomes aware of its existence. The carcinoma may cause the person to cough and feel a dull persistent pain on one side of the chest: 85% of cancers.

2. Sarcoma: grows in the muscles, bones, fat, supportive and connective body tissues: 2% of cancers. 3. Lymphoma: cancer cells travel through the lymph system. Sometimes the entire lymph itself becomes cancerous: 5-6% of cancers. 4. Leukemia: cancer of bone marrow-the red sponge-like material where blood is made. It is mostly in children: 3-4% of cancers. One of the major sources of cancer is the body itself. Researchers have found evidence that some people are programmed to get cancer before birth.

These people may have a certain gene inside each cell that triggers the body to begin growing a cancer at a certain age. That may explain why some cancers seem to run in a family. History of CancerCancer has plugged humans since ancient times. It has been found in the bones and skulls of ancient Egyptians and Peruvian mummies as far back as 3000 BC. Hypocrites, around 400 BC, first used carcinoma, from the Greek word karkinoma, meaning “crab”. Around 200 AC Clarissmus Galen, was the first that referred to fleshy tumors as sarcomas. IN 1936, Johnnes M·ler used microscope to distinguish between normal and cancer cells.

Cancer is the uncontrolled growth of cells due to mutations in the proto-oncogenes and tumor suppressor genes. Unlike normal cells, cancer cells divide even when they do not receive a signal to divide and they can divide indefinitely. In addition, …

Initially, when scientists were beginning to grasp the concept of DNA and its storage genes, they believed certain genes present in the DNA sequence would be expressed and those who were not originally expressed would remain hidden throughout that organisms’ …

The role of regulation of gene expression is becoming more and more complex and integrated in the structural phenotype of the cells and the organism as a whole. This regulatory control is most evident and indeed most variable in the …

Cancer is a disease both caused by genetics and environmental factors. Each person has either proto-oncogenes or oncogenes. These are the genes that are responsible for regulating cell division. When a person has an oncogene it is a mutation of …

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