DNA is the basis for heredity. This lies rolled up in the form of chromosomes. Humans have 46 chromosomes. Of these, 23 are from the mother and 23 from the father. Except for germ cells, every cell in the human body has 46 chromosomes.
The number of chromosomes differs from species to species, but provides no information about the development of the organism. For example, blackbirds have over 80 chromosomes. The chromosomes occur in homologous pairs.
This means that two chromosomes are responsible for reproducing genetic information. Of the 46 chromosomes, two are called gonosomes. Your job is to set the gender. Here are the chromosomes in the cell nuclei, which are also referred to as the carrier of the genetic material.
If you unroll your structure, this would measure a length of about 2 meters. As part of cell division, the chromosomes also divide. This process is called mitosis or meiosis. The meiosis takes place in the germ cells, egg cell and sperm, the mitosis in all other body cells. The existing chromosomes are reproduced in such a way that they are always identical.
Chromosomes consist of two halves. These are often not the same length and are called chromatids. In the middle, the halves interlock. Chromosomes that unite at one end of the chromoatides are called submetacentric. The arms are shortened. The place where the halves unite is called the centromere.
In the course of mitosis or meisoe, the chromatids divide at the centromere and are drawn to the cell ends. Since every cell carries genetic information, it is necessary that it be duplicated during cell division. The chromatids consist of rolled-up DNA. This stacks again in a double strand.
In the double strand, two base pairs are combined with each other. These face each other and are complementary. Of the four different base pairs, only two ever fit together. The arms of the chromosome are usually in a position that looks like an X.
Chromosomes have two special tasks: First, they determine the gender of the child, and second, they provide him with all the genetic information that is necessary. These include, for example, the color of eyes and hair. The inherited information comes from mother and father. That's why the chromosomes always appear in pairs. The traits are inherited dominant or recessive.
Since the same characteristic is passed on from mother and father and thus, for example, the information would be available for two different eye colors, one of the features must prevail in the further course. In addition to external events, the chromosomes are also responsible for the development of skills and behavior. In addition, they can transmit existing diseases to the newborn. On the other hand, inherited properties, such as a large muscle mass, are not inherited.
In sex, only the 23rd chromosome plays a role, the so-called gonosome. The sex chromosomes differ in X and Y chromosomes. In women, there are two X chromosomes, and men have an X and Y chromosome. Accordingly, the sperm decides which gender is inherited, because women have only X chromosomes and therefore can not pass on their Y chromosome.
Without the chromosomes, heredity could not take place. Accordingly, great complications may arise if number or shape are not correct.
Particularly well-known is the Down syndrome, also called Trisomy 21 in professional circles. The name already gives information about this problem: instead of twice the 21st chromosome exists 3 times. Affected children have developmental disorders as well as physical ailments, such as heart defects.
In the Turner syndrome, however, a chromosome is missing. The disease can affect girls only because the missing chromosome is the second X chromosome. Patients report dwarfism and infertility. It is noticeable in disorders of chromosomes that in women who have two X chromosomes, damage to one of the gonosomes can be compensated.
This is not the case for men. The fact can be explained by the fact that men possess only one X chromosome, whereby defects on this can not be compensated. This results in hereditary diseases that affect almost only men. Examples include red-green disease, hemophilia or Duchenne muscular dystrophy. In very few cases, the patients are women.
In general, defects in chromosomes can arise during cell division, the fusion of egg and sperm cells or in the formation of germ cells. Such a process results in too many or too few chromosomes. It is also possible that the structure of the chromatid is damaged. In addition, it can not be ruled out that certain external influences have a negative effect on the chromosomes. These include, for example, radiation or some chemicals.
Diseases that are based on a chromosome defect can not be treated. It is only possible to mitigate the resulting consequences.Tags: