One of the worst things in the universe is radiation. It can cause cancer, and can easily kill people. They were used in atomic bombs to kill tons of people. Also, if humans want to colonize on Mars, they will have to protect themselves from radiation.
The first idea is to create a transparent shield generator around Mars that can deflect radiation and have a tiny opening for spaceships to come in. This shield can also deflect lasers and other weapons, and will only let sunlight pass.
The second idea is to make suits for everybody that will deflect radiation, but it would look trash and be super heavy. This is something already in use in science labs. But, mass production would be hard because some of its materials are rare.
The last idea is to live underground of mars, so that it would be hard for radiation to pass through the land. Electricity would be hard to make underground, so people can put solar panels on the land. Also, planting would be easier underground, as it is super windy on Mars. They will require some lighting as well.
To sum it up, there are other options than gene editing to colonize Mars. One idea is to make a transparent shield that protects us. Another idea is to make everybody wear a radiation-proof vest. Lastly, we can live underground.