chromosomes - is the structural and functional elements of the human cells that contain genes.These units are capable of a number of cell-painted at the time of cell division.Chromosomes are shaped rods, strands, loops, etc.. Along its length, these elements are mixed.They consist of the centromere, short and long arm, secondary constriction, satellite, thread spindles, chromonemata.Location of that part of the chromosome as the centromere, affects what will be the shape of the unit cell of the series.In that case, if the part is located at the end of the structural and functional elements, it will rodlike.Finding such a portion as the centromere, mid affects chromosome that takes the form of equal-studs.If the part in question is located on the side of the center, the structural and functional element becomes a stud with different shoulders.
Generally, there are 4 types of structure of chromosomes.The first type are telotsentricheskie structural and functional elements.Second - acrocentric (second arm is very short and almost imperceptible).The third type are submetacentric chromosome, the shape of which resembles the letter "L".Finally, the fourth type - metacentric.Chromosomes of this type are the so-called arms which are equal in length.In addition, elements such napomminayut letter and at the same time a symbol of victory "V".
It should be noted that each of nucleated somatic human cell comprises twenty-three pairs of chromosomes, which are linear.In addition, there are a large number of copies of mitochondrial DNA (deoxyribonucleic acid).
should say a few words about sex structural and functional elements of the human cells.This Y- and X-chromosome.The first contains about 58 base pairs, carries 78 genes and thus has a high rate of mutation due to the environment in which it is located.This sex chromosome is able to be transmitted only through sperm.These, in turn, is a huge number of cell divisions occurring during gametogenesis.Place sperm - is vysokookislitelnaya Wednesday testicles, stimulating amplification process such as mutating.The second chromosome has about 150 million base pairs.It carries almost 1400 genes.Men have one X- and one Y-chromosome.Women have a different "set".They have two X-chromosomes.One gets the girl from her mother, and the other is inherited from my father's mother, that is,grandmother on his father.
question often arises as to which chromosomes are called homologous and non-homologous.The answer is as follows.Thus, substantially homologous chromosomes.It paired the structural and functional elements found in a diploid cell.Homologous chromosomes are characterized in that every one of them from one and from the other parent.Such elements have a similar nucleotide sequence over the entire length.This means that the homologous chromosomes have the same genes, which are arranged in the same sequence.It is worth noting that the study of such topics is not only interesting but also very useful in life, because of his body better to know as much as possible.
should add that homologous chromosomes constantly have the same type.For example, they can be tselotsentricheskimi, submetacentric, acrocentric, metacentric.Non-homologous chromosomes contain genes that are dissimilar.In addition, these structural and functional elements are conjugated during meiosis.Non-homologous chromosomes independently perform combining in the cell.This was proven during the study of inheritance of characteristics.Also, this information was obtained by direct cytology method.
information listed above will help to have a basic understanding of chromosomes as a whole.
