The circular molecule formed by fusing two replicons, one possessing a transposon, the other lacking it. The cointegrate structure has two copies of the transposon located at both replicon junctions, oriented as direct repeats. The formation of a cointegrate structure is thought to be an obligatory intermediate in the transposition process. The donor molecule (containing the transposon) is nicked in opposite strands at the ends of the transposon by a site-specific enzyme. The recipient molecule is nicked at staggered sites. Donor and recipient strands are then ligated at the nicks. Each end of the transposon is connected to one of the single strands protruding from the target site, thereby generating two replication forks. When replication is completed, a cointegrate structure is formed, which contains two copies of the transposon oriented as direct repeats. An enzyme required in the formation of the cointegrate structure is called a transposase. The cointegrate can be separated into donor and recipient units each of which contains a copy of the transposon. This process is called resolution of the cointegrate, and it is accomplished by recombination between the transposon copies. The enzyme involved in resolution is called a resolvase.
Subjects: Genetics and Genomics.