contain the heredity information. The chromosomes are highly condensed coiled chromatin fibres packed with the DNA (Deoxyribonucleic acid) that forms the genetic material. Genes are segments of DNA, which are responsible for the inheritance of a particular phenotypic character. Each gene is present at a specific position on a chromosome called its locus .
During cell division, the genetic information present in the genes are passed from one generation to another. . . Structure of a Chromosome The chromosomes are thin, long and thread like structures consisting of two identical strands called sister chromatids.
They are held together by the centromere. Each chromatid is made up of spirally coiled thin structure called chromonema. The chromonema has number of bead-like structures along its length which are called chromomeres. The chromosomes are made up of DNA,RNA, chromosomal proteins (histones and non-histones) and certain metallic ions.
These proteins provide structural support to the chromosome . A chromosome consists of the following regions Primary constriction: The two arms of a chromosome meet at a point called primary constriction or centromere . The centromere is the region where spindle fibres attach to the chromosomes during cell division. Secondary constriction: Some chromosomes possess secondary constriction at any point of the chromosome.
They are known as the nuclear zone or nucleolar organizer (formation of nucleolus in the nucleus). Telomere: The end of the chromosome is called telomere. Each extremity of the chromosome has a polarity and prevents it from joining the adjacent chromosome. It maintains and provides stability to the chromosomes.
Satellite: Some of the chromosomes have an elongated knob-like appendage at one end of the chromosome known as satellite. The chromosomes with satellites are called as the sat-chromosomes . Telomeres act as aging clock in every cell. Telomeres are protective sequences of nucleotides found in chromosomes.
As a cell divides every time, they become shorter. Telomeres get too short to do their job, causing our cells to age. Figure . Structure of chromosome .
. Types of Chromosomes based on the position of Centromere Based on the position of centromere, the