Mitosis is divided into five phases: 1. Interphase: The DNA in the cell is copied in preparation for cell division, this results in two identical full sets of chromosomes. Outside of the nucleus are two centrosomes, each containing a pair of centrioles, these structures are critical for the process of cell division.
During interphase, microtubules extend from these centrosomes. Prophase: The chromosomes condense into X-shaped structures that can be easily seen under a microscope. Each chromosome is composed of two sister chromatids, containing identical genetic information.
The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on. At the end of prophase the membrane around the nucleus in the cell dissolves away releasing the chromosomes. The mitotic spindle, consisting of the microtubules and other proteins, extends across the cell between the centrioles as they move to opposite poles of the cell.
Metaphase: The chromosomes line up neatly end-to-end along the centre equator of the cell. The centrioles are now at opposite poles of the cell with the mitotic spindle fibres extending from them.
The mitotic spindle fibres attach to each of the sister chromatids. Anaphase: The sister chromatids are then pulled apart by the mitotic spindle which pulls one chromatid to one pole and the other chromatid to the opposite pole. Telophase: At each pole of the cell a full set of chromosomes gather together.
Lifestyle factors Viruses linked with cancer, such as the human papilloma virus HPV , being spread from person to person through sexual intercourse. The chemical carcinogens in cigarette smoke increasing the risk of lung cancer. Alcohol intake is linked with certain cancers. Exposure to ultraviolet radiation , part of which is ionising , during sunbathing or outdoor activities, leading to the development of skin cancers.
A poor diet with increased fat and salt intake, as well as the consumption of certain foods, can increase the risk of cancer. Industrial and environmental factors Exposure to ionising radiation, like ultraviolet radiation in sunlight, increases the risk factor. Exposure to chemical carcinogens such as those in cigarette smoke. We call this process "cell division" and "cell reproduction," because new cells are formed when old cells divide. The ability of cells to divide is unique for living organisms.
Cells divide for many reasons. For example, when you skin your knee, cells divide to replace old, dead, or damaged cells. Cells also divide so living things can grow. When organisms grow, it isn't because cells are getting larger. Organisms grow because cells are dividing to produce more and more cells. In human bodies, nearly two trillion cells divide every day. Watch cells divide in this time lapse video of an animal cell top and an E.
The video compresses 30 hours of mitotic cell division into a few seconds. Video by the National Institute of Genetics. You and I began as a single cell, or what you would call an egg. By the time you are an adult, you will have trillions of cells. That number depends on the size of the person, but biologists put that number around 37 trillion cells. Yes, that is trillion with a "T. In cell division, the cell that is dividing is called the "parent" cell.
The parent cell divides into two "daughter" cells. The process then repeats in what is called the cell cycle. Cells regulate their division by communicating with each other using chemical signals from special proteins called cyclins. These signals act like switches to tell cells when to start dividing and later when to stop dividing.
It is important for cells to divide so you can grow and so your cuts heal. It is also important for cells to stop dividing at the right time. If a cell can not stop dividing when it is supposed to stop, this can lead to a disease called cancer. Some cells, like skin cells, are constantly dividing. We need to continuously make new skin cells to replace the skin cells we lose. Did you know we lose 30, to 40, dead skin cells every minute? That means we lose around 50 million cells every day.
This is a lot of skin cells to replace, making cell division in skin cells is so important. Other cells, like nerve and brain cells, divide much less often. Depending on the type of cell, there are two ways cells divide—mitosis and meiosis. Each of these methods of cell division has special characteristics.
During prophase, the replicated pairs of chromosomes condense and compact themselves. The pairs of chromosomes that have been replicated are called sister chromatids, and they remain joined at a central point called the centromere.
A large structure called the mitotic spindle also forms from long proteins called microtubules on each side, or pole, of the cell. During prometaphase, the nuclear envelope that encloses the nucleus breaks down, and the nucleus is no longer separated from the cytoplasm.
Protein formations called kinetochores form around the centromere. The mitotic spindle extends from the poles and attaches to the kinetochores.
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