<P> Like the components of other intermediate filaments, the lamin monomer contains an alpha - helical domain used by two monomers to coil around each other, forming a dimer structure called a coiled coil . Two of these dimer structures then join side by side, in an antiparallel arrangement, to form a tetramer called a protofilament . Eight of these protofilaments form a lateral arrangement that is twisted to form a ropelike filament . These filaments can be assembled or disassembled in a dynamic manner, meaning that changes in the length of the filament depend on the competing rates of filament addition and removal . </P> <P> Mutations in lamin genes leading to defects in filament assembly cause a group of rare genetic disorders known as laminopathies . The most notable laminopathy is the family of diseases known as progeria, which causes the appearance of premature aging in its sufferers . The exact mechanism by which the associated biochemical changes give rise to the aged phenotype is not well understood . </P> <P> The cell nucleus contains the majority of the cell's genetic material in the form of multiple linear DNA molecules organized into structures called chromosomes . Each human cell contains roughly two meters of DNA . During most of the cell cycle these are organized in a DNA - protein complex known as chromatin, and during cell division the chromatin can be seen to form the well - defined chromosomes familiar from a karyotype . A small fraction of the cell's genes are located instead in the mitochondria . </P> <P> There are two types of chromatin . Euchromatin is the less compact DNA form, and contains genes that are frequently expressed by the cell . The other type, heterochromatin, is the more compact form, and contains DNA that is infrequently transcribed . This structure is further categorized into facultative heterochromatin, consisting of genes that are organized as heterochromatin only in certain cell types or at certain stages of development, and constitutive heterochromatin that consists of chromosome structural components such as telomeres and centromeres . During interphase the chromatin organizes itself into discrete individual patches, called chromosome territories . Active genes, which are generally found in the euchromatic region of the chromosome, tend to be located towards the chromosome's territory boundary . </P>

Chromosomes are found in what part of the cell