Human Y chromosome variation in normal and abnormal babies and their fathers

C-banded chromosome preparations were obtained from cord blood from normal newborns and venous blood from abnormal newborns and the corresponding fathers. There is significant heterogeneity between individuals in euchromatin and especially heterochromatin lengths of the Y chromosome. The average dimensions of the Y of fathers of normal and abnormal babies do not differ. Y chromosomes from cord blood appear more condensed than from venous blood and the consequences are not removed by the use of the Y/F index. Such differences have not been considered in reported apparent variation in the size of the Y chromsome in relation to criminality.