[Genetics of longevity].
It is possible to use different studies to demonstrate the genetic component of a phenotype. From the beginning of the century, many authors have studied the possible genetic transmission of longevity. The study of genealogies of ascendants first, and then of descendants of elderly individuals shows that the age at death incorrelated in people belonging to the same family. Finally, the studies carried out on monozygot and dizygot twins have made it possible to estimate that this genetic component accounts for approximately 10% of the individual's lifespan. Research on congenic mice which differ only by the chromosomic region of the Major Histocompatibility Complex (MHC) implies that this particular region might have an effect on longevity. However, the study of several alleles of the MHC indicates a complex sex-dependent influence. Several other chromosomic regions are also implied. As far as human beings are concerned, several research teams have worked on the HLA region. Once again, the situation is still far from clear.