Make sure you understand that GMOs are genetically engineered organisms. They are considered to be transgenic because they contain the the DNA from two separate species. You need to be aware of the role of Restriction enzymes in cutting DNA. DNA Ligase in joining two separate strands of DNA together and the role of Plasmids - small loops of bacterial DNA as vectors . Vectors are structures that transport the DNA from one organism into another.
This is very helpful to help you form an opinion to help with evaluation style questions.
CRISPR is a technique you will be hearing a lot about over the next few years.