Approximately one of each 200 babies is born with a chromosomic anomaly. Syndrome of Down, that causes that a baby is born with an additional chromosome 21, is one of the more common chromosomic anomalies, whose effects are known by most of people. The children affected with this syndrome present/display different degrees from mental delay, characteristic face characteristics and, frequently, cardiac defects and other problems. Aside from the syndrome of Down, many other chromosomic anomalies exist. Some of them are less severe but others are more serious and they even can produce the of the baby before his birth. Many of the children who have chromosomic anomalies, although not all, are characterized to have mental delay, incapacities of learning or problems of conduct. A deeper knowledge of the chromosomes can turn out useful to understand ample range of problems that can cause the chromosomic anomalies.
What are the chromosomes?
The chromosomes are tiny structures with filament form that are presents in the cells of the organism. They contain the considered amount of 30,000 to 35,000 pairs of human genes, that determine characteristics like the color of the eyes and the hair and that, in addition, control the growth and the development of each component of our physical and biochemical system. All we normally have 23 pairs of chromosomes, or 46 altogether. Generally, we inherited one of the chromosomes of the pair of our mother and other of our father. Nevertheless, sometimes a baby can be born with a greater or smaller amount of chromosomes, or with one or more broken chromosomes or an alteration in his structure. The errors in the amount or structure of the chromosomes cause a great variety of birth defects, that can be from slight to severe.
Which are the causes of the chromosomic anomalies?
Generally, the chromosomic anomalies are been from an error produced during the development of an ovum or esperm�tica cell. The causes of these errors are not known. (March of Dimes offers its support to a number of scholarship holders that is trying to discover the causes of these errors to help to prevent the chromosomic anomalies). Nevertheless, to where it is known, nothing of which makes or lets do anyone of the parents before the pregnancy or during his development it can cause a chromosomic anomaly in his son. The esperm�ticas cells and the ova are different from the other cells of the organism. These reproductive cells only have 23 individual chromosomes. When an ovum is united with a cell esperm�tica- and begins pregnancy-they form an ovum fertilized with 46 chromosomes. But some times something leaves bad before the pregnancy begins. During the process of cellular division, an error takes place that causes that an ovum or esperm�tica cell is with an amount of chromosomes greater or smaller than the normal thing.
When this cell with an incorrect amount of chromosomes is united with a normal ovum or esperm�tica cell, the embryo has a chromosomic anomaly. A common type of chromosomic anomaly is the trisom�a, that takes place when a person has three copies, instead of two, of a specific chromosome. The syndrome of Down is a trisom�a example. Generally, the people with syndrome of Down have three copies of chromosome 21. In most of the cases, the embryos that they have an incorrect amount of chromosomes do not survive. In these cases, the pregnant woman has a spontaneous abortion, frequently without knowing it. Until the 70 percent of the produced spontaneous abortions during the first trimester of the pregnancy she must to chromosomic anomalies. Also other s can take place, generally before the pregnancy begins, that could alter the structure of one or more chromosomes. Although a person has the normal amount of chromosomes, can happen that small segments of one or more chromosomes are eliminated, duplicate itself, is reversed, altered her normal location or they interchange with part of another chromosome. These structural alterations also can produce the loss of the pregnancy and defects of birth.
