So, what the heck is that symbol flying around significantly on Heroes? And how come it keeps appearing? Is it significant also that it looks like an RNA molecule?

Here’s all the references it has had in Heroes thus far, as listed on Wikipedia. The symbol has appeared…
- formed by flotation devices in a pool at a crime scene
- scrolling in Chandra Suresh’s program
- in a drawing by Peter Petrelli
- in Isaac Mendez’s paintings
- on a post-it in Mohinder’s apartment
- on a geometry textbook owned by Claire Bennet
- on pictures in Sylar’s apartment
- on Niki’s back whenever she becomes Jessica
- on future Hiro’s sword
- on Chandra Suresh’s book, Activating Evolution
- on Wonders!, the comic by Isaac Mendez
- on the Haitian’s necklace
- on a Greyhound bus
There is a second symbol in Heroes – two parallel lines. It appears on the necks of Heroes who have been abduced and "wiped" by the Haitian.

[...] Superhero Profiles has in depth coverage one of tv’s hottest shows – Heroes. From recaps and spoilers to posts on the actors and more. Like, what is that darn symbol that keeps cropping up? [...]
The symbol signifies the identity of the path left behind from Hiro as he travels through time, it shows the riff caused from his travelling where things have been changed due to the space time continum been altered. it is a way of identifying the change in the present and a symbol for universal identification of all heros
Sean that’s definitely a different way of looking at the symbol. It has been appearing from different time periods so maybe it is a time rift. As far as reality is, Hayden is still going strong with Stephen.
umm that person who wants to know what the symbol means it means its everlasting power. it is also a god sent symbol.
What is the name of the symbol?
The helix is a combination of two Japanese symbols that, when put together like this, mean “Godsend.”