The tiniest of living organisms called protozoa, and protozoa. Some of them are barely visible to the naked eye, but most are microscopic in size. That is why they are studied under a microscope.
The representative of the simplest, such as amoeba, consists of a tiny drop of jelly-like fluid called the protoplasm. This drop of protoplasm is separated from the water in which living amoeba, very thin membrane. Protoplasm, separated by a membrane from the external environment, is called a cell.
Although the amoeba and has a microscopic size, it performs all the essential life functions. It can capture food particles that are less than its volume, digest them and throw out undigested remnants. It can detect the danger and in this case, the move to avoid it. It can grow, and when she turn into a certain size, it can be divided, so that in place of an amoeba, two are formed. When the amoeba is divided into two parts, new daughter cells will have all the characteristics of the old parent cell.
It would be reasonable to assume that if we understood how the cell divides into two cells, while preserving all its features, it could be a starting point for examining how these characteristics are transferred from larger organisms, creatures such as humans.
Simplest consist of a single cell. Animals more than simple, composed of many cells, closely adjacent to each other. Because each of these cells is approximately the same size as the cell protozoa, then in order to form a large animal, they require quite a lot. Man, for example, consists of trillions and trillions of microscopic cells. Each human cell consists of protoplasm, each surrounded by a cell membrane. Animals, composed of many cells, called metazoa. Man also belongs to the metazoa.
Single cell protozoa – a sort of jack of all trades. She can do everything a little. In metazoa cells have different specialization. In man, for example, have long, thin cells that make up muscle tissue, which become shorter and thicker, when the muscle is strained. There are nerve cells with an uneven contour, which transmit messages from one part of the body to another. There are skin cells, which serve as protection for the remaining resilient parts of the body.
Some of these different cells, such as those that make up the brain and nerves have become so specialized that they lost the ability to divide. Other types of cells, however, continue to divide throughout life, or at least, can share, whenever it becomes necessary. For example, the outer skin cells gradually wear out throughout their lives. For this reason, cells in deeper layers of skin continually grow and divide to replace lost cells.
The process of dividing human cells is almost the same as the process of cell division in protozoa. Human cells maintain their characteristics after dividing the same way, kai and cell protozoa. In fact, the process of division is approximately the same in all cells. To investigate this process, let’s take a closer look at the cage.
Initially, all cells that grow and divide, are composed of two parts. Somewhere within the cell, often near its center, there is a small patch of protoplasm that is separated from the rest of the cell membrane more subtle and delicate than the outer membrane of the cell. This inner part of cells called the nucleus. The protoplasm surrounding the nucleus, called cytoplasm.
Of these two parts of the cell nucleus is the most important. We assume that the amoeba is divided in two by a microscopic needle tip in a way that one half contains the whole kernel, while the other half contains the nucleus. Half of the kernel will restore the missing part and will then continue to live a normal life, growing and sharing. Half of the kernels without live for only a short time, but then dries up and dies. It does not grow and will never be divided.
So, now let’s dwell more in detail at the very core. If we make very thin slices of tissues of certain organs and place them under a microscope, we can see individual cells and even, perhaps, cell nuclei within the cells. If we confine ourselves to looking, it is nothing special in the nucleus, we do not see. But we will not be limited to these.
The nucleus, like the cell as a whole, is composed of many different substances. Some chemical substances when added to water, enclosing a plate with a tissue, can penetrate the cells and connect with some but not all substances that are there. These chemicals are sometimes painted in one or another color. Adding the necessary chemical in the cellular tissue, we paint some parts of the cells and leave intact the other part of it. When, for example, a drug called Feulgen reagent is added to the cell, the scattered parts of the kernel becoming bright red color (color Feulgen). These parts are called chromatin (from the Greek word meaning “color”). If the drug is added to the cells at various stages of division, the behavior of chromatin may become visible to us, and that his behavior is the key to the situation of interest to us.