What is the center of the DNA strand?

It exhibits traits and metabolic instructions of the cell.

Explanation:

A DNA strand is a thin long molecule, with an average width of just around two nanometers. The remarkable thinness of the DNA strands allows them to be bundled very tightly fitted inside cells. Once DNA has been replicated adequately during the process of cell division, it is further wrapped together under a mechanism known as supercoiling. A non-condensed DNA is further condensed during supercoiling using a special protein known as a histone. A part of DNA packed around a large cluster of histones is called a nucleosome. Additional condensation leads to a chromosome or the most compact type of DNA that fits into the nucleus. It is also worth noting that this wrapping does not merely align DNA into a cell, but serves other objectives such as protecting DNA, thus ensuring metabolic instructions to the cell.

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave