{TAIL ~ The excised segment} can be {HEAD ~ as long as 28 nucleotides}, or more, and as little as one nucleotide 
{ TAIL ~ The excised segment } can be { HEAD ~ as long as 28 nucleotides } , or more , and as little as one nucleotide
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH