How is the long dna molecule able to fit inside the microscopic cell nucleus?

DNA undergoes series of coiling and compaction to fit into the nucleus.

Explanation:

A DNA molecule consists of two polynucleotide chains composed of four nucleotide subunits (Adenine, Guanine Cytosine, Thymine). Each of these chains is known as DNA strand. However, this long strands of DNA cannot enter into the genome.

Hence, the long DNA strands are coiled around a set of proteins called HISTONES, which support its stucture. This coiling forms a NUCLEOSOME. The nucleosome is the unit of Chromatins which are formed when the nucleosome becomes further coiled and stacked together. The Chromatin then undergoes another series of coiling and folding, with the help of additional proteins, to form thread-like structures called Chromosomes.

These chromosomes composed of long strands of DNA coiled together become able to fit into the cell's nucleus.

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