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')

public double GetFraction(
	byte item
)

Public Function GetFraction ( 
	item As Byte
) As Double

public:
double GetFraction(
	unsigned char item
)

member GetFraction : 
        item : byte -> float