Describe the normal process of cell division (mitosis), and explain how this process is affected in the abnormal growth of tumours
Cell division is important as it allows cells to reproduce also they divide so that organs can grow and be repaired. “In the form of cell division called Mitosis, one cell divides into two daughter cells, each of them then complete but smaller than the original cell.”  The cell cycle is a seven stage process by which a cell duplicates itself and divides in two. The first stage is Prophase where chromosomes become visible and the nucleus begins to break down and disappear by the end of this phase. Uncoiled DNA molecules called chromatin coil up to form chromosomes which doubles from 46 to 92. Finally paired centrioles begin to move to opposite ends of the cell to begin the dividing process. In the prometaphase microtubules in the cell attach to centrosomes located on either side of the cell forming spindle fibres. In metaphase, “the chromosomes are moved by the spindle fibres to form a perfect row at the centre of the spindles, midway between the centrioles.”  The next stage is Anaphase where the chromosomes are pulled away by the spinals towards one of the centrioles and “by the end of anaphase, an identical set of forty-six chromosomes is present at each pole.”  In Telophase the chromosomes has reached poles and the microtubules disappear. Nuclear envelopes also become evident around chromosomes and the cell begins to divide. A process called Cytokinesis splits the cells cytoplasm where an actin contractile ring tightens the middle region of the cell. This then develops two separate yet identical daughter cells, “the spindle fibres disintegrate, nuclear envelops are formed around the chromosomes in each cell and the chromatin returns to its loosely coiled state.”  Finally an interphase period begins when the new cell has been formed allowing it to grow, this ends they are ready to divide again. The...
Please join StudyMode to read the full document