The cell growth, inheritance and containment is controlled by its DNA deoxyribonucleic acid. DNA is a highly complex molecule manufactured in the cell nucleus and serves as the cell's "brain.
In a human cell, the DNA is arranged in 46 distinct sections called chromosomes. They are arranged in pairs, 23 chromosomes from each biological parent. Together, the 46 chromosomes contain more than , genes.
A gene is a segment of DNA that determines the structure of a protein , which is needed for development and growth as well as carrying out vital chemical functions in the body.
Like the chromosomes, genes are arranged in pairs — one gene from the mother and one from the father. Each gene occupies a specific location on a chromosome. Through a number of biochemical steps, each gene tells a cell to make a different protein.
Some genes instruct the cell to manufacture structural proteins, which serve as building blocks. Other genes tell the cell to produce hormones, growth factors or cytokines , which exit the cell and communicate with other cells. Still other genes tell the cell to produce regulatory proteins that control the function of other proteins or tell other genes when to turn "on" or "off.
Cells divide only when they receive the proper signals from growth factors that circulate in the bloodstream or from a cell they directly contact. For example, if a person loses blood, a growth factor called erythropoietin , which is produced in the kidneys, circulates in the bloodstream and tells the bone marrow to manufacture more blood cells.
When a cell receives the message to divide, it goes through the cell cycle , which includes several phases for the division to be completed. Checkpoints along each step of the process make sure that everything goes the way it should. Many processes are involved in cell reproduction and all these processes have to take place correctly for a cell to divide properly.
If anything goes wrong during this complicated process, a cell may become cancerous. But cancer that is thought to be cured can still come back even years later. This is why some doctors prefer to say that the cancer is in remission. Remission means there are fewer signs and symptoms of a disease such as cancer or that they have completely gone away. Home Cancer information What is cancer? How cancer starts, grows and spreads. See topics What is cancer?
Types of cancer Human body Immune system Lymphatic system Blood and bone marrow Endocrine system and hormones Female sex organs and reproductive system Male sex organs and reproductive system How cancer starts, grows and spreads Types of tumours Genes and cancer Stage and grade Prognosis and survival What causes cancer?
What is cancer? Diagram of cell division. Diagram of how cancer grows. Diagram of how cancer spreads. Where cancer can spread and staging. Why does cancer sometimes come back? Cure or remission. References American Society of Clinical Oncology.
What is Cancer? American Society of Clinical Oncology. What is Metastasis? Cancer Research UK. How Cancers Grow. Cancer starts with changes in one cell or a small group of cells. Usually, we have just the right number of each type of cell. This is because cells produce signals to control how much and how often the cells divide.
If any of these signals are faulty or missing, cells might start to grow and multiply too much and form a lump called a tumour. A primary tumour is where the cancer starts. Some types of cancer, called leukaemia , start from blood cells. They don't form solid tumours. Instead, the cancer cells build up in the blood and sometimes the bone marrow. For a cancer to start, certain changes take place within the genes of a cell or a group of cells. All cells have a control centre called a nucleus.
Inside the nucleus are chromosomes made up of thousands of genes. Genes contain long strings of DNA deoxyribonucleic acid , which are coded messages that tell the cell how to behave. Each gene is an instruction that tells the cell to make something.
This could be a protein or a different type of molecule called RNA ribonucleic acid. Together, proteins and RNA control the cell. They decide:.
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