Question: How were the original pictures of DNA taken?

Edward Guy answered on 20 Mar 2023:

These were originally taken using x-rays rather than light (the method is called x-ray crystallography), and was done originally by a scientist called Rosalind Franklin. If you shine light at a crystal, you get a pattern of dots of light as the crystal deflects the light. The same things happen if you shine x-rays onto a crystal. However, if the crystals are not perfectly formed and regular, the pattern gets messed-up. So, the trick was how to form DNA into regular ‘crystals’. Once that was done, the x-rays made a pattern on photographic film. It didn’t look anything like the real thing, though, because the next step was to use maths to calculate from the pattern of dots, what the actual crystal looked like.

If I am being a sneaky scientist and answering the question literally, the first DNA was seen by ordinary light microscopy (it’s easy to see chromosones in cells with an ordinary light microscope and chromosones are DNA!).

However, the first pictures of DNA strands were probably taken using electron microscopes (so, that’s a third way of getting pictures, the first two above being using x-rays or using light). As electron microscopes improved, it became possible to see the helix structure predicted by Rosalind Franklin in her original x-ray crystallography work.