It has long been held that each person has one genome, meaning each of their cells share the same basic genetic material. Following decades of rare cases that disputed this, the tenet is now being upended by the discovery of a greater number of individuals with multiple genomes. Called chimerism, the condition is being discovered more now due to researchers’ search for it and the use of sequencing. It can result from twins sharing genetic material through a mixed blood supply or some of a baby’s DNA being left in the mother’s womb. It can also be the result of mosaicism, which occurs when an embryo acquires the genetic changes of a mutated cell. Some of these mutations can cause cancer, as in the case of leukemia. Although researchers believe most of the mutations are not harmful, their role in common diseases is being studied. Another area of research is forensics, where new ways to confirm identity are being explored. The findings have affected genetic counseling, as DNA test results from one cell may exclude a person’s other genomes.

Source: New York Times