<P> Apoptosis is a controlled process in which the cell's structural components are destroyed, resulting in death of the cell . Changes associated with apoptosis directly affect the nucleus and its contents, for example, in the condensation of chromatin and the disintegration of the nuclear envelope and lamina . The destruction of the lamin networks is controlled by specialized apoptotic proteases called caspases, which cleave the lamin proteins and, thus, degrade the nucleus' structural integrity . Lamin cleavage is sometimes used as a laboratory indicator of caspase activity in assays for early apoptotic activity . Cells that express mutant caspase - resistant lamins are deficient in nuclear changes related to apoptosis, suggesting that lamins play a role in initiating the events that lead to apoptotic degradation of the nucleus . Inhibition of lamin assembly itself is an inducer of apoptosis . </P> <P> The nuclear envelope acts as a barrier that prevents both DNA and RNA viruses from entering the nucleus . Some viruses require access to proteins inside the nucleus in order to replicate and / or assemble . DNA viruses, such as herpesvirus replicate and assemble in the cell nucleus, and exit by budding through the inner nuclear membrane . This process is accompanied by disassembly of the lamina on the nuclear face of the inner membrane . </P> <P> Initially, it has been suspected that immunoglobulins in general and autoantibodies in particular do not enter the nucleus . Now there is a body of evidence that under pathological conditions (e.g. lupus erythematosus) IgG can enter the nucleus . </P> <P> Most eukaryotic cell types usually have a single nucleus, but some have no nuclei, while others have several . This can result from normal development, as in the maturation of mammalian red blood cells, or from faulty cell division . </P>

How many chromosomes in the nucleus of a cell