Replication in research means using the same method and methodology in proximity to the original research work.
It helps in bringing, validating and proving the original study is up-to-date. It may be done using the same exact methods in a different cultural settings, location or different research subjects to determine if the original experimental results is up-to-date.
The reason why is because A only pairs with T, and G only pairs with C. So, if you have a strand with GGTCTA, the only possible pairing for that to replicate is CCAGAT.
There are some examples where human hormone genes are excised and placed into bacterial DNA. An example of this is Human Growth Hormone, which is mass-produced for human use by bacteria.
