Next in terms of rising cost ($100 per participant) and quality is to sample whole blood. The total yield of DNA from one such sample can last a laboratory for many years, even with fairly intensive use (i.e., lots of genotyping). Most critically, blood samples are the only sample source which can, if the additional costs are available, be transformed to yield immortalized cell lines. These cell lines provide a long-term source of DNA, RNA, protein or cell lysates for future work. They also require regular maintenance by skilled staff. Although this final step means the samples from a project will last for as long as they are properly maintained, it is probably not viable for most social scientists unless they have access to either a core facility or a collaborating lab.
