Chromosome

 Strasburger discovered thread-like structures in 1875 which appeared during cell division. The term chromosome was given by Waldeyer in 1888 since these structures showed an affinity for basic dyes and could be stained deeply, while the cytoplasm took little or no stain. The term chromosome is derived from the Greek word 'chroma' which means 'color' and 'soma' which means 'body'. Chromosomes are the organized structures of DNA and proteins found in cells. They are thread-like structures located inside the nucleus of animal and plant cells. Chromosomes are composed of a single molecule of DNA with many copies of five types of histones. Histones are protein molecules and are rich in lysine and arginine residues, they are positively charged.

Hence, they bind tightly to the negatively charged phosphates in the DNA sequence. A small number of non-histone proteins are also present, these are mostly transcription factors.

Chromosomes play an important role that ensures DNA is copied and distributed accurately in the process of cell division. In most organisms, chromosomes are arranged in pairs in the nucleus of the cell.

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