function DNA = randomDNA_(len,numberGaps)
% generate a random DNA sequence of length len with a number of gaps
% specified by numberGaps.
% Gaps are represented by the symbol '-' in the sequence.
% K. Ming Leung, Nov. 13, 2008
ACGT = 'ACGT';  % a string containing all the allowed symbols
% generate a DNA sequence
DNA = ACGT(RandIntegers_(1,len,1,4));
DNA(RandIntegers_(1,numberGaps,1,len)) = '-';
