What are the importance and structure of chromosomes ?

The chromosomes

The chromosomes are thread like bodies present in the cell’s nuclei , and they represent the genetic material of the living organisms , They are not visible in the cell’s nucleus not even under a microscope , When the cell is not dividing  However , the DNA that makes up the chromosomes becomes more tightly packed during the cell division and it is visible under a microscope .

Chromosomes structure

The  chromosomes  consist of two connected threads , each thread is called the chromatid , The two chromatides are connected at a point known as the centromere which is the point of connection of the two chromatides of chromosome during the cell division .

The centromeres help to keep the chromosomes properly aligned during the complex process of the cell division , As the chromosomes are copied in the preparation for production of a new cell , The centromere serves as an attachment site for the two halves of each replicated chromosome , known as sister chromatids .

The DNA molecule is packaged into thread like structures called the chromosomes in the nucleus of each cell , Each chromosome is made up of DNA tightly coiled many times around the proteins called the histones that support its structure .



Each chromosome has a constriction point called the centromere which divides the chromosome into two sections  or “arms” The short arm of the chromosome is labeled the “p arm” , The long arm of the chromosome is labeled the “q arm” , The location of the centromere on each chromosome gives the chromosome its characteristic shape , and it can be used to help describe the location of the specific genes .

Each chromatid consists of protein and a nucleic acid called DNA which carries the genes that carry the genetic traits of the living organism , DNA is the nucleic acid that forms the chromosomes that present in the cell nucleus and it carries the genes .

The bodies of multicellular  living orgnisms contain two kinds of cells which are the somatic cells and the reproductive cells , The somatic cells are all the body cells except the reproductive cells .

The somatic cells in the humans and the animals such as the cells of the liver , the cells of the kidney , And the somatic cells in the plants such as the cells of the roots , the cells of the stem , the cells of the leaves  .

The cell nucleus is responsible for the cell division because it contains the genetic material of the living organisms which consists of a number of chromosomes that have the main role in the cell division .

The somatic cells contain two sets of chromosomes ( one inherited from the father and the other from the mother ) , The number of chromosomes in the somatic cells is a diploid number ( 2 N ) , while in the gametes [ the male gametes ( the sperms ) and the female gametes ( ova ) ]is a haploid number ( N ) .

All the somatic cells contain 23 chromosomes in the human , The humans have 23 pairs of chromosomes ,  And 46 chromosomes for a total , Each species of plants and the animals has a set number of chromosomes .

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