[Further study on the nature of a multicentury small Y chromosome (author's transl)].

A study of a small Y chromosome, found in a family line established in Canada since 1664, and traced back in France in some descendants of a sixteenth century ancestor related to the canadian one, has shown, by C-, G- and Q-banding techniques, that it was deleted of the q12 segment. This study suggests that the del(Y)(q12) results from the oldest known chromosome aberration.