Replication
in
Duplex
Rod
Prokaryote
Chromosome
IIn the virus T7 the chromosome is a duplex rod of about 40,000 base pairs. This size permits a coding capacity of about 25 genes. The parental strands separate at a point about 17% from one end. This site is called the growing point. Bidirectional DNA synthesis takes place from this point.
Separation of the strands results in a replication inter mediate called the eye form. In a more advanced stage of replication the proximal growing point reaches the end of the DNA rod, resulting in the Y form. Sometimes a second round of synthesis may be initiated before completion of the first round. This results in the formation of a secondary eye at a point 17% from the end of the arms of the Y.
