It is always surprising how many of our students don't seem to know their right hand from their left. It is more surprising how many scientists don't know their right-handed helixes from their left [local]. Most students have difficulty and need help [local]. Here's a way to help them. Have them twist a pipe cleaner around a pencil or pen to form a helix. There will be a mixture of right and left handed helixes. Ask them to identify which they have produced. Then tell them to turn it upside down and see if it is the same or the other form.

Also, don't let all the fun about the publication of the wrong structures of DNA make your students forget that one form of left-handed DNA [local] (Z-DNA) may exist in the cell.