In a new study, researchers have described why older male fruit flies are more likely to pass on mutations to their offspring, which may shed light on the risk of inherited disease in humans. The male reproductive system serves as a hotspot for the emergence of new genes. Perhaps this explains why more new mutations are inherited from fathers than from mothers.
However, this does not explain why older fathers pass on more mutations and diseases to children than younger ones. The mechanisms that might underlie these well-documented trends have long remained a mystery, the study said.
Scientists at Rockefeller University in the US studied mutations that occur during the production of sperm from germ cells, known as spermatogenesis. They found that mutations are common in the testes of both young and old fruit flies, but are more abundant from the start in older flies.
The findings were published in the journal Nature Ecology & Evolution.
Moreover, many of these mutations appear to be removed in younger fruit flies during spermatogenesis by the body’s genome repair mechanisms—but fail to be fixed in the testes of older flies.
“We sought to test whether the older germline is less efficient at repairing mutations, or whether the older germline begins to mutate more,” said first author Evan Witt.
“Our results suggest that it is actually both. At each stage of spermatogenesis, there are more mutations per RNA molecule in older flies than in younger flies,” Witt said.
Genomes are kept in order by several repair mechanisms.