It's not an apostrophe, it's a single quote. The article title is:

> Smoking 'causes hundreds of DNA changes'

I'm guessing HN trimmed the closing quote to change it to:

> Smoking 'causes hundreds of DNA changes

It's now been changed to:

> Smoking “causes hundreds of DNA changes”

Those are weird quotes too, not the normal ". There are lots of different quote characters. :)

Pedants will probably like this magazine: http://media-cache-ak0.pinimg.com/736x/df/b7/74/dfb7741e5e84...