Gets the fraction of occurrences of a specific sequence char. This method does not perform any calculations to group counts of ambiguous symbols with corresponding unambiguous symbols. So the minimum G-C content of a DNA sequence would be calculated as GetFraction('G') + GetFraction('C') + GetFraction('S')

Gets the fraction of occurrences of a specific symbol. This method does not perform any calculations to group counts of ambiguous symbols with corresponding unambiguous symbols. So the minimum G-C content of a DNA sequence would be calculated as GetFraction('G') + GetFraction('C') + GetFraction('S')