Every cell contains DNA, which is in fact the vital information (genetic code) needed to construct and maneuver a human body. DNA is structured into units called genes. An eukaryotic cell nucleus contains a lot of DNA and protein that get together to form a chromosome. Therefore, the chromosome is the major carrier of genetic information. All species have different numbers of chromosomes and diffe[...]DOWNLOAD REFERAT
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When cells reach maturity, they must either stop growing and remain as they are, or divide and reproduce themselves. Some cells like the nerve and muscle cells in the human body don't divide but stay the same as they reach maturity, this makes them rarer and more finite. Other cells divide when they reach maturity through the Mitosis or Meiosis types of cell division. The cells that do divide do so in what is called the cell cycle, the cycle of a cell life from one division to the next. A cell cycle from one division to the next is also called a generation as it is with human beings from one set of parents to the children. (Solomon et al 2002).
Most cells both eukaryotic and prokaryotic divide through the Mitosis processes which is asexual. An example of this might be eukaryotic human skin cells and or prokaryotic bacteria; they replicate themselves exactly but not sexually. Eukaryotic cells are different that the prokaryotic cells however because they contain much more DNA and their reproduction process is more complicated. Eukaryotic cells also reproduce sexually through Meiosis in more developed (higher on the evolutionary scale) plants and animals. During, the sexual type of cell division called Meiosis special cells called gametes (eggs and sperm) come together to create a finished product called a zygote (fetus). (Solomon et al 2002). « mai multe referate din Biologie