What exactly is N in cell culture and animal experiments?

In this observational meta-science study, we surveyed a random sample of published animal experiments from 2011 to 2016 where interventions were applied to parents but effects examined in the offspring. We assessed whether entity–intervention pairs that contributed to the sample size (N) constituted true replication or pseudo replication. We found that only 22% of studies replicated the correct entity–intervention pair.