What type of spells are you talking about? If it's any type of spell that's going to change your DNA in any way, such as growing wings, becoming a mermaid or anything other than human, magick cannot alter your DNA. If it's one of the spells on this site, not all of these spells are legit/will work. It's best to create your own spells, because then they are customized to you and usually work better. You also need to know how to focus energy into your spell and direct it to affect the outcome of your intent.
Hope this helps.