Experimental approaches for the detection of chromosomal malsegregation occurring in the germline of mammals.

Existing and newly proposed methods to detect the induction of heritable aneuploidy are summarized, and their favorable and unfavorable features discussed. Among the tests involving direct chromosomal examination, those involving study of pronuclear chromosomes at first cleavage are judged to be the most universally informative and reliable, provided tertiary trisomy can be ruled out. Measurement of postmidterm (fetal) death is proposed as a trisomy prescreen that can be readily combined with a dominant-lethal test. Among the genetic procedures for identifying the results of malsegregation events, direct detection of aneuploids has a number of advantages over complementation methods, in which only a fraction of the products of aneuploid gametes is detectable. Direct detection of aneuploids must, however, be restricted to sex chromosomes if postnatal animals are examined. A genetic marker system to detect autosomal trisomies in fetuses is proposed. An examination of experimental parameters that might maximize induction of malsegregation leads to the recommendation to include preleptotene among exposed germ-cell stages.