The scientists, led by Pedro Nuno Moreira, warned that “semen samples collected in human infertility clinics are frequently contaminated with bacteria,” according to their report that appeared in the journal Human Reproduction. The title of their research, Inadvertent Transgenesis by Conventional ICSI in Mice, highlights the crux of the problem: that DNA from the bacteria actually alters the genetic structure of the DNA in the resulting embryos.
The term transgenesis refers to the altering of an organism’s genetic code by the transfer of a gene or genes from another species or breed. Mixing sperm with foreign DNA has also been proposed as a way to intentionally alter the genetics of the offspring.