Length of a Human DNA Molecule

The chromosomes in the nucleus of a cell contain all the information a cell needs to carry on its life processes. They are made up of a complex chemical (a nucleic acid) called deoxyribonucleic acid, or DNA for short. Scientist's decoding of the chemical structure of DNA has led to a simple conceptual understanding of genetic processes. DNA is the hereditary material of all cells. It is a double-stranded helical macromolecule consisting of nucleotide monomers with deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T). In the chromosomes of a cell, DNA occurs as fine, spirally coiled threads that in turn coils around another, like a twisted ladder.

The DNA molecule is threaded so fine that it is only possible to see it under high powerful electron microscopes. To get a sense of exactly how long an uncoiled DNA molecule is compared to a typical cell, a cell is magnified 1000 times. At this scale, the total length of all the DNA in the cell's nucleus would be 3 km -- the equivalent distance of the Lincoln Memorial to the capital in Washington, DC.

The human genome comprises the information contained in one set of human chromosomes which themselves contain about 3 billion base pairs (bp) of DNA in 46 chromosomes (22 autosome pairs + 2 sex chromosomes). The total length of DNA present in one adult human is calculated by the multiplication of

(length of 1 bp)(number of bp per cell)(number of cells in the body)

(0.34 × 10-9 m)(6 × 109)(1013)

2.0 × 1013 meters

That is the equivalent of nearly 70 trips from the earth to the sun and back.

2.0 × 1013 meters = 133.691627 astronomical units
133.691627 / 2 = 66.8458135 round trips to the sun

On the average, a single human chromosome consists of DNA Molecule that is almost 5 centimeters.