The significance of the double helix is that it allows DNA to replicate itself.  After it has copied itself, it can transfer that copy from parent to offspring.  The significance of DNA to us humans is that we are able to use it to trace back to our ancestors. A couple of reasons to why a triple helix DNA strand wouldn't work was because it was unable to make copies of itself as a double helix does and Rosalind Franklin had X-ray pictures to prove that the DNA strand couldn't be a triple helix. Watson~Crick model's novel feature is a double helix.  After research and many tests, they were finally able to find the structure of DNA.  It was a Double Helix. If you know the DNA sequence of one side then you can just guess what the other side is because the opposite side is always the exact opposite of the other side.  For example, if it is A-G-G-T-U-G then the opposite side will be G-A-A-U-T-A.