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
Merkel cell polyomavirus another study, 45 of 53 (85%) Merkel cell tumors were positive. Sequencing of the virus from Merkel cell cancers reveals that it generally has tumor-specific mutations that truncate the MCV T antigen. These mutations (which are not found in native virus obtained from nontumor sites) eliminate the T antigen helicase, preventing the integrated virus from replicating independently from the host cancer cell. The tumor is a "dead-end host" for MCV. Normally, the virus exists as circular episome (or plasmid) within the cell and its DNA is packaged into viral capsids and transmitted to other cells. In tumors, the viral DNA