| [the duffy system: a population genetics study in portugal, guinea-bissau and brazil]. | 2225 blood samples from portugal (classed according to historical provinces), 301 blood samples from guinea-bissau (classed in tribes) and 697 blood samples from brazil (classed according to colour of skin) have been tested in the duffy system. the portuguese seem to be a sufficiently uniform and autonomous population. this is also true for the (non-rejected) blood-samples from guinea-bissau. the brazilians differ in accordance with their colour of skin. the expected relations between portugal a ... | 1985 | 3909949 |