Explanation

According to Watson and Crick’s DNA model, DNA exists as double helix in which two polynucleotide chains are coiled about one another in a spiral way (a right handed spiral). The base pairs in DNA are stacked 3.4Å apart with 10 base pairs in a turn (360${^\circ}$) on the double helix. Therefore, if the length of DNA has 45,000 base pairs, DNA molecule will take 4,500 complete turns.