Nuclear DNA the bases are held together by hydrogen bonds. Nuclear DNA and mitochondrial DNA differ in many ways, starting with location and structure. Nuclear DNA is located within the nucleus of eukaryote cells and usually has two copies per cell while mitochondrial DNA is located in the mitochondria and contains 100-1,000 copies per cell. The structure of nuclear DNA chromosomes is linear with open ends and includes 46 chromosomes containing 3 billion nucleotides. Mitochondrial DNA chromosomes usually have closed, circular structures, and contain for example 16,569 nucleotides in human. Nuclear DNA is diploid, ordinarily inheriting the DNA from two parents, while
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.