Tail bleeding time assays. Littermates from GP VI^het × GP VI^het crosses were subjected to tail bleeding assays. A 2- to 3-mm portion of distal tail was removed from 5-week-old animals and the cessation of bleeding time was recorded. Following a determination of the bleeding time, genotype analysis was performed and the data are presented correlating the bleeding time with the genotype. Data obtained from individual animals are shown.