Cell cycle levels in S and at their lowest near mitosis. Cell cycle The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication of its DNA (DNA replication) to produce two daughter cells. In bacteria, which lack a cell nucleus, the cell cycle is divided into the B, C, and D periods. The B period extends from the end of cell division to the beginning of DNA replication. DNA replication occurs during the C period. The D period refers to the stage between the end of DNA replication and
Transfer DNA Transfer DNA The transfer DNA (abbreviated T-DNA) is the transferred DNA of the tumor-inducing (Ti) plasmid of some species of bacteria such as "Agrobacterium tumefaciens" and "[[Agrobacterium rhizogenes](actually an Ri plasmid)]". The T-DNA is transferred from bacterium into the host plant's [[cell nucleus|nuclear]] DNA [[genome]]. The capability of this specialized tumor-inducing (Ti) plasmid is attributed to two essential regions required for DNA transfer to the host cell. As the T-DNA is bordered by 25-base-pair repeats on each end. Transfer is initiated at the right border and terminated at the left border and requires the "vir" genes of the Ti plasmid.