This is an idea I've been toying with for some time. My idea is a human race where FTL is relatively easy, so colonization is widespread. Its not entirely wild frontier. Habitable worlds are identified and a "Citadel" is constructed. Basically a building that is large enough to house the initial population, has the infrastructure to support them and can act as a seat of government when the colony begins expanding and the population has alternate housing.
Strict birth-control is enforced during the initial phase of colonization, because colonists must first expand their infrastructure and be able to live independent of the Citadel. After the colony is deemed stable enough, the birth control enforcement is lifted.
Now we come to the meat and potatoes. Assuming a fairly small initial population (say 200-400) where the workforce is supplemented with machinery, would it then be a good idea to ensure genetic diversity within the colony by also bringing a cargo of sperm- and egg cells? Basically couples who wish to have children may need to have one or both of their "genetic input" replaced with the "cargo gene pool".