Organisms with linear chromosomes have to solve the problem that DNA replication makes them shorter. This is due to the fact that DNA polymerase can only add bases to the terminal 3'-OH of a DNA chain. The DNA replication initiation complex uses RNA primers to provide the initial 3'-OH and to initiate "lagging" strand synthesis. While one strand can be copied all the way to the end of a chromosome, the other, lagging strand, must be primed at short intervals in order to provide a 3' OH group for DNA polymerase as the replication fork advances through a chromosome. The problem at the end of a chromosome then is that the lagging strand has nothing for the primer to bind to. Without some kind of solution, each replication cycle would result in a shorter chromosome.