The four bases found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T).
In genetics, GC-content is the percentage of Guanine (G) and Cytosine (C) bases on a DNA molecule that are either guanine or cytosine. 
Given a DNA sequence (a string) return the GC-content in percent, rounded up to 2 decimal digits for Python, not rounded in all other languages.
For more information about GC-content you can take a look to [wikipedia GC-content](https://en.wikipedia.org/wiki/GC-content).
**For example**: the GC-content of the following DNA sequence is 50%:
"AAATTTCCCGGG".
**Note**: You can take a look to my others bio-info kata [here](http://www.codewars.com/users/nbeck/authored)
def gc_content(seq):
    return round(sum(c in 'GC' for c in seq) / len(seq) * 100, 2) if len(seq) else 0.0
def gc_content(seq):
    return round(sum(c in 'GC' for c in seq) / len(seq) * 100, 2) if len(seq) else 0.0