'Mice homozygous for a Robertsonian translocation (for example, a fusion between chromosomes 6 and 16; strain A) were crossed to a strain homozygous for a second Robertsonian translocation (for example, between chromosomes 16 and 17; strain B). From this cross, male offspring were selected that carried both Robertsonian translocations (compound heterozygotes) and mated to wild-type mice lacking any Robertsonian translocation. Between 7 to 40% of the resulting progeny [the exact percentage depended on the strain background, the stage of embryogenesis analyzed, and identity of the translocation chromosome (8)] were trisomic for the chromosome common to the two Robertsonian translocations due to a meiotic non-disjunction event in the male germline.' quoted from a paper.
Dear Chanwoo
Heterozygotes for complex translocations will show many metaphase I cell with 1 pentavalent plus 1 univalent (besides the normal bivalents not involved in the translocations). This is because one of the chromosomes (usually a small one, or one involved in the 2 translocations) will form no chiasmata during prophaseI. Such univalent chromosomes behave independently from the pentavalent during anaphase I, which can easily lead to partial (or even full) trisomies.
You can check my first publication (Goicoechea et al, 1987 Genome; downloadable here at RG), to visualize the univalents behaviour at metaphase I and anaphase I in heterozygotes for one translocation (in rye cells).
Hope this helps
Pablo
(Goicoechea et al, 1987 Genome; downloadable here at RG)
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