Repeats

[Steve Jones]

There are two basic types of repeats that are found in the 
worm.

	 Firstly there are the local repetitive regions.  This category 
includes tandemly repeated sequences and inverted repeats.  In C. elegans
about 4% of the current genomic sequence is occupied by the arms of inverted 
repeats whilst around 9% is between such arms. A further 2.2% of the current 
genomic sequence is made up of tandem repeats. These figures are depend strongly 
however on the stringency of the search criteria e.g. how identical do the 
arms of an inverted repeat have to be and how far apart can they be. 
In the same way, how divergeant can the individual units of a tandem repeat 
be and still be determined as part of a tandem array. The above figures are 
calculated using relatively stringent criteria. 

	Secondly, there are the repeat families or long range repeats i.e.
similar sequences found numerous times throughout the genome. Currently 
we have defined 17 of these families which in total occupy about 1.7% of the current 
genomic sequence. Many more such families are currently being characterised. 

Steven Jones 
The Sanger Centre
http://www.sanger.ac.uk/