<p>can someone explain for me that why there are a few gaps in reference genome??</p>

<p>thanks!</p>

<p>The simple answer is that certain stretches of a genome contain sequence that is difficult to sequence, mainly due to repetitive regions, tracks of the same base, GC composition, closed DNA, etc.  Searching Google for "gaps genome" brings up a whole host of references about the causes of gaps and the attempts to close them. </p>
