If your dna is already in solution then spinning down will move all of the wetting on the tube sides into the solution at the bottom which will minimise the loss of water to evaporation in storage although small volumes will evaporate even when stored in a freezer.

Your dna will remain in solution during spinning and storage because addition of salt and alcohol is needed for dna precipitation. Once your dna is dissolved it should stay dissolved even in freezing and thawing

Paul Rutland Thank you so much for your Answer. but after spining after performing a dilution isn't that going to change the concentration of that volume that I take for further analysis because while spining DNA molecules with go to the bottom of the tube. at the end I will find myself with a concentration less than what prepared in the first tube (after dilution)

What you say is very important when using thawing solutions of any kind where the salts and dna thaw first and leave a floating ice lump which then melts and leaves pure water at the top of the sample Nchioua Zakariya . If the sample is not mixed after thawing then you remove just water from the top part of the sample but over strength dna from the bottom of the tube.

This does not apply to your situation. Your sample is refrigerated so freezing is not an issue so the reagents remain in solution. Spinning at any speed in any centrifuge that exists in your laboratory will never spin dissolved dna molecules down....this requires ultracentrifugation at enormous g forces. In normal spinning speeds the random molecular motion of the water molecules will keep the dna or any other molecule suspended in solution.

Just to reiterate what Paul Rutland said, spinning a solution of DNA will NOT make the DNA go to the bottom. And the spinning in this context is really just to collect all the liquid from the tube walls, so you only need to spin for a few seconds.

Thank you so much for your answers. Now I understand.