The DNA isolated through normal procedure is single strand or double strand .How can we identify in seeing the Agrose gel images?
Typically DNA is double stranded after isolation. Unless you heated the DNA to 95 C in which case you couldnt run a gel, since it would melt. You could see RNA on a gel but only in denaturing conditions.
Hope that answers your question.
Also you might want to change the title of your post to something like. "Question about Double stand vs Single strand DNA"
Molecular Biology is fairly vague and a large topic